Process for the preparation of an alkylene glycol

ABSTRACT

The invention provides for the utilization of microchannel apparatus in a process for the preparation of an alkylene glycol by the reaction of a corresponding alkylene oxide and water.

REFERENCE TO PRIOR APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.60/752,977 filed Dec. 22, 2005.

FIELD OF THE INVENTION

The present invention relates to improvements in process operationsinvolving particularly hydrocarbons. The process improvements envisagedfind especial application in the production of olefin oxide from olefinand oxygen and in its optional further conversion.

BACKGROUND OF THE INVENTION

When operating on a commercial scale, process operations have to meet anumber of important design criteria. In the modern day environment,process design has to take account of environmental legislation and keepto health and safety standards. Processes that utilize or producedangerous chemicals pose particular problems and often, in order tominimize risks of explosion or reaction runaway, such process operationshave to be run at conditions that are not optimal; this increases therunning costs of a plant (the operational expenditure or OPEX). Suchprocesses may also have to utilize more equipment than is necessary justto perform the process; this leads to an increase in building costs (thecapital expenditure or CAPEX).

There is an on-going need to provide process operations that can reduceCAPEX and OPEX costs and particularly without increasing the risk ofdamage to the plant and danger to the public and/or to the process plantworkers.

SUMMARY OF THE INVENTION

The present invention provides for the utilization of microchannelapparatus in process operations. Such apparatus have previously beenproposed for use in certain specific fields of application but have notpreviously been proposed to provide the combination of reduced CAPEXand/or OPEX with maintained or reduced plant safety risks.

The present invention provides a process for the preparation of analkylene glycol by the reaction of a corresponding alkylene oxide andwater, which process comprises

a) flowing the alkylene oxide and water through a microchannel reactor,wherein the oxide and water undergo an exothermic reaction to form thecorresponding alkylene glycol,

b) transferring heat from the microchannel reactor to a heat transfermedium, and

c) recovering the alkylene glycol product from the microchannel reactor.

In another aspect the present invention provides a process for thepreparation of a mono-alkylene glycol by the reaction of a correspondingalkylene oxide and water, which process comprises

a) reacting the alkylene oxide and water in a first reactor under afirst set of conditions and in the presence of a catalyst so as toachieve vapor phase conversion to the mono-alkylene glycol,

b) altering the conditions in the first reactor to a second set ofconditions whereby glycols deposited on the surface of the catalyst areremoved,

c) re-establishing the first set of conditions in the first reactor inorder to repeat step a), and

d) recovering the mono-alkylene glycol from a vapor phase mixtureproduced in step a) and/or step b).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic drawing of a microchannel reactor and its mainconstituents.

FIG. 2 shows a schematic drawing of a typical example of a repeatingunit which comprises process microchannels and heat exchange channelsand its operation when in use in the practice of the invention. Amicrochannel apparatus or reactor utilized in this invention maycomprise a plurality of such repeating units.

FIG. 3 shows a schematic drawing of an example of a process for thepreparation of ethylene oxide.

FIG. 4 shows a schematic drawing of an example of a process for thepurification of ethylene oxide.

FIG. 5 shows a schematic drawing of an example of a typical process forthe removal of combustible volatile contaminant materials from a processstream.

FIG. 6 shows a schematic drawing of an example of a glycol productionunit according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides, in a number of aspects, processes thatutilize microchannel apparatus. In a number of these processes themicrochannel apparatus may house a chemical reaction and optionally mayalso contain catalytic components; in other processes the microchannelapparatus are utilized for physical operations. Hereinafter a discussionof such apparatus is given and reference is made generally to“microchannel reactors”; this term will be understood to encompassmicrochannel apparatus whether utilized for physical processes or forchemical reaction processes, with or without a catalytic component.

Microchannel reactors suitable for use in this invention and theiroperation have been described in WO-A-2004/099113, WO-A-01/12312,WO-01/54812, U.S. Pat. No. 6,440,895, U.S. Pat. No. 6,284,217, U.S. Pat.No. 6,451,864, U.S. Pat. No. 6,491,880, U.S. Pat. No. 6,666,909, U.S.Pat. No. 6,811,829, U.S. Pat. No. 6,851,171, U.S. Pat. No. 6,494,614,U.S. Pat. No. 6,228,434 and U.S. Pat. No. 6,192,596. Methods by whichthe microchannel reactor may be manufactured, loaded with catalyst, andoperated, as described in these references, may generally be applicablein the practice of the present invention.

With reference to FIG. 1, microchannel reactor 100 may be comprised of aheader 102, a plurality of process microchannels 104, and a footer 108.The header 102 provides a passageway for fluid to flow into the processmicrochannels 104. The footer 108 provides a passageway for fluid toflow from the process microchannels 104.

The number of process microchannels contained in a microchannel reactormay be very large. For example, the number may be up to 10⁵, or even upto 10⁶ or up to 2×10⁶. Normally, the number of process microchannels maybe at least 10 or at least 100, or even at least 1000.

The process microchannels are typically arranged parallel, for examplethey may form an array of planar microchannels. Each of the processmicrochannels may have at least one internal dimension of height orwidth of up to 15 mm, for example from 0.05 to 10 mm, in particular from0.1 to 5 mm, more in particular from 0.5 to 2 mm. The other internaldimension of height or width may be, for example, from 0.1 to 100 cm, inparticular from 0.2 to 75 cm, more in particular from 0.3 to 50 cm. Thelength of each of the process microchannels may be, for example, from 1to 500 cm, in particular from 2 to 300 cm, more in particular from 3 to200 cm, or from 5 to 100 cm.

The microchannel reactor 100 additionally comprises heat exchangechannels (not shown in FIG. 1) which are in heat exchange contact withthe process microchannels 104. The heat exchange channels may bemicrochannels. The microchannel reactor is adapted such that heatexchange fluid can flow from heat exchange header 110 through the heatexchange channels to heat exchange footer 112.

The heat exchange channels may be aligned to provide a flow in aco-current, counter-current or, in some aspects, preferablycross-current direction, relative to a flow in the process microchannels104. The cross-current direction is as indicated by arrows 114 and 116.

Each of the heat exchange channels may have at least one internaldimension of height or width of up to 15 mm, for example from 0.05 to 10mm, in particular from 0.1 to 5 mm, more in particular from 0.5 to 2 mm.The other internal dimension of height or width may be, for example,from 0.1 to 100 cm, in particular from 0.2 to 75 cm, more in particularfrom 0.3 to 50 cm. The length of each of the heat exchange channels maybe, for example, from 1 to 500 cm, in particular from 2 to 300 cm, morein particular from 3 to 200 cm, or from 5 to 100 cm.

The separation between each process microchannel 104 and the nextadjacent heat exchange channel may be in the range of from 0.05 mm to 5mm, in particular from 0.2 to 2 mm.

In some embodiments of this invention, there is provided for first heatexchange channels and second heat exchange channels, or first heatexchange channels, second heat exchange channels and third heat exchangechannels, or even up to fifth heat exchange channels, or even furtherheat exchange channels. Thus, in such cases, there is a plurality ofsets of heat exchange channels, and accordingly there may be a pluralityof heat exchange headers 110 and heat exchange footers 112, whereby eachset of heat exchange channels may be adapted to receive heat exchangefluid from a heat exchange header 110 and to deliver heat exchange fluidinto a heat exchange footer 112.

The header 102, footer 108, heat exchange header 110, heat exchangefooter 112, process microchannels 104 and heat exchange channels mayindependently be made of any construction material which providessufficient strength, optionally dimensional stability, and heat transfercharacteristics to permit operation of the processes in accordance withthis invention. Suitable construction materials include, for example,steel (for example stainless steel and carbon steel), monel, titanium,copper, glass and polymer compositions. The kind of heat exchange fluidis not material to the present invention and the heat exchange fluid maybe selected from a large variety. Suitable heat exchange fluids includesteam, water, air and oils. In embodiments of the invention whichinclude a plurality of sets of heat exchange channels, such sets of heatexchange channels may operate with different heat exchange fluids orwith heat exchange fluids having different temperatures.

A microchannel reactor of use in the invention may comprise a pluralityof repeating units each comprising one or more process microchannels andone or more heat exchange channels. Reference is now made to FIG. 2,which shows a typical repeating unit and its operation.

Process microchannels 210 have an upstream end 220 and a downstream end230 and may comprise of a first section 240 which may optionally, forcertain aspects of the present invention, contain a catalyst (notshown). First section 240 may be in heat exchange contact with firstheat exchange channel 250, allowing heat exchange between first section240 of process microchannel 210 and first heat exchange channel 250. Therepeating unit may comprise first feed channel 260 which leads intofirst section 240 through one or more first orifices 280. Typically oneor more first orifices 280 may be positioned downstream relative toanother first orifice 280. During operation, feed may enter into firstsection 240 of process microchannel 210 through an opening in upstreamend 220 and/or through first feed channel 260 and one or more firstorifices 280.

Process microchannels 210 may comprise a second section 340 which may ormay not be adapted to contain a catalyst. Second section 340 ispositioned down stream of first section 240. Second section 340 may bein heat exchange contact with second heat exchange channel 350, allowingheat exchange between second section 340 of process microchannel 210 andsecond heat exchange channel 350. In some embodiments second section 340is adapted to quench product obtained in and received from first section240 by heat exchange with a heat exchange fluid in second heat exchangechannel 350. Quenching if required may be achieved in stages by thepresence of a plurality of second heat exchange channels 350, forexample two or three or four. Such a plurality of second heat exchangechannels 350 may be adapted to contain heat exchange fluids havingdifferent temperatures, in particular such that in downstream directionof second section 340 heat exchange takes place with a second heatexchange channel 350 containing a heat exchange fluid having a lowertemperature. The repeating unit may comprise second feed channel 360which leads into second section 340 through one or more second orifices380. During operation, feed may enter into second section 340 fromupstream in process microchannel 210 and through second feed channel 360and one or more second orifices 380.

The first and second feed channels 260 or 360 in combination with firstand second orifices 280 or 380 whereby one or more first or secondorifices 280 or 380 are positioned downstream to another first or secondorifice 280 or 380, respectively, allow for replenishment of a reactant.Replenishment of a reactant can be utilized in some embodiments of thisinvention.

Process microchannels 210 may comprise an intermediate section 440,which is positioned downstream of first section 240 and upstream ofsecond section 340. Intermediate section 440 may be in heat exchangecontact with third heat exchange channel 450, allowing heat exchangebetween intermediate section 440 of the process microchannel 210 andthird heat exchange channel 450.

In some embodiments, process microchannel 210 may comprise a thirdsection (not drawn) downstream of second section 340, and optionally asecond intermediate section (not drawn) downstream of second section 340and upstream of the third section. The third section may be in heatexchange contact with a fourth heat exchange channel (not drawn),allowing heat exchange between the third section of the processmicrochannel 210 and fourth heat exchange channel. The secondintermediate section may be in heat exchange contact with a fifth heatexchange channel (not drawn), allowing heat exchange between the secondintermediate section of the process microchannel 210 and fifth heatexchange channel. The repeating unit may comprise a third feed channel(not drawn) which ends into the third section through one or more thirdorifices (not drawn). Typically one or more third orifices may bepositioned downstream relative to another third orifice. Duringoperation, feed may enter into the third section from upstream inprocess microchannel 210 and through the third feed channel and the oneor more third orifices.

Each of the feed channels may be a microchannel. They may have at leastone internal dimension of height or width of up to 15 mm, for examplefrom 0.05 to 10 mm, in particular from 0.1 to 5 mm, more in particularfrom 0.5 to 2 mm. The other internal dimension of height or width maybe, for example, from 0.1 to 100 cm, in particular from 0.2 to 75 cm,more in particular from 0.3 to 50 cm. The length of each of the feedchannels may be, for example, from 1 to 250 cm, in particular from 2 to150 cm, more in particular from 3 to 100 cm, or from 5 to 50 cm.

The length of each of the sections of the process microchannels may beselected independently of each other, in accordance with, for example,the heat exchange capacity needed or the quantity of catalyst which maybe contained in the section. The lengths of the sections mayindependently be at least 1 cm, or at least 2 cm, or at least 5 cm. Thelengths of the sections may independently be at most 250 cm, or at most150 cm, or at most 100 cm, or at most 50 cm. Other dimensions of thesections are defined by the corresponding dimensions of processmicrochannel 210.

The microchannel reactor of this invention may be manufactured usingknown techniques, for example conventional machining, laser cutting,molding, stamping and etching and combinations thereof. The microchannelreactor of this invention may be manufactured by forming sheets withfeatures removed which allow passages. A stack of such sheets may beassembled to form an integrated device, by using known techniques, forexample diffusion bonding, laser welding, cold welding, diffusionbrazing, and combinations thereof. The microchannel reactor of thisinvention comprises appropriate headers, footers, valves, conduit lines,and other features to control input of reactants, output of product, andflow of heat exchange fluids. These are not shown in the drawings, butthey can be readily provided by those skilled in the art. Also, theremay be further heat exchange equipment (not shown in the drawings) fortemperature control of feed, in particular for heating feed or feedcomponents, before it enters the process microchannels, or fortemperature control of product, in particular for cooling product, afterit has left the process microchannels. Such further heat exchangeequipment may be integral with the microchannel reactor, but moretypically it will be separate equipment. These are not shown in thedrawings, but they can be readily provided by those skilled in the art.

Where catalyst is present, it may be in any suitable form to beaccommodated in one or more of the process microchannels. Such catalystmay be installed by any known technique in the designated section of theprocess microchannels. The catalyst may be in solid form and form apacked bed in the designated section of the process microchannels and/ormay form a coating on at least a portion of the wall of the designatedsection of the process microchannels. Alternatively the catalyst may bein the form of a coating on inserts which may be positioned in thedesignated section of the microchannel apparatus. Coatings may beprepared by any suitable deposition method such as wash coating or vapordeposition. Where a catalyst is comprised of several catalyticallyeffective components, deposition may be achieved by deposition of afirst catalytic component, e.g. a metal or metal component, on at leasta portion of the wall of the designated section of the processmicrochannels with the deposition of one or more additional catalystcomponents on at least the same wall prior to, together with, orsubsequent to that of the first component.

In some embodiments the catalyst may be homogeneous and not in solidform in which case the catalyst may be fed to the designated section ofthe process microchannels together with one or more components of therelevant feed or process stream and may pass through the microchannelsalong with the reaction mixture or process stream.

The present invention in certain aspects finds especial application in aprocess for the manufacture of alkylene oxide, and especially ethyleneoxide, by the direct epoxidation of alkylene using oxygen or air, seeKirk-Othmer Encyclopedia of Chemical Technology, 3^(rd) edition, Volume9, 1980, pages 445 to 447. In the air-based process, air or air enrichedwith oxygen is employed as a source of the oxidizing agent while in theoxygen-based processes, high purity (at least 95 mole %) oxygen isemployed as the source of the oxidizing agent. Currently mostepoxidation plants are oxygen-based. The epoxidation process may becarried out using reaction temperatures selected from a wide range.Preferably the reaction temperature within the epoxidation reactor is inthe range of from 150° C. to 340° C., more preferably in the range offrom 180 to 325° C. The reaction is preferably carried out at a pressureof in the range of from 1000 to 3500 kPa.

The mixing of oxidants and hydrocarbon materials is a hazardous process.Where the oxidant is particularly oxygen gas, the mixing process has tobe strictly controlled to minimize the mixing volume of oxygen gasfollowing addition to the hydrocarbon material.

Considering the mixing of oxygen gas and a hydrocarbon material such asethylene, a mixture of the two materials has a minimum and a maximumoxygen level between which the mixture can become explosive. Prior tomixing, the oxygen stream has an oxygen level that exceeds the upperexplosion limit, following mixing the aim would be for the oxygen levelto be below the lower explosion limit. However during mixing there willinevitably be a stage where the mixture will have an oxygen level thatlies in the explosive region.

It is therefore advantageous to have a mixing process that minimizes thelength of time that an oxidant-hydrocarbon mixture exists in therelevant explosive region.

In the commercial production of ethylene oxide, oxygen is reacted withethylene in extremely large volumes. In commercial operations thisreaction is currently performed by addition of oxygen gas to a gasstream that contains ethylene and a ballast gas which may comprise oneor more of nitrogen, carbon dioxide and methane. Additionally the gasstream may also contain other gases such as ethane, oxygen, and argonfollowing recycle, see U.S. Pat. No. 3,119,837 and EP-A-893,443 forexample. Minimizing the risk of explosion following addition ofsignificant volumes of oxygen gas to the gas stream is of prime concern.Specific devices have been developed to ensure rapid mixing and tominimize the volume of gas in the gas stream that exists in theexplosive region i.e. to minimize the volume of not fully mixed gases.One such device is a mixing device in the shape of a ring or ‘doughnut’,see Research Disclosure No. 465117, Research Disclosure Journal, January2003, page 106, Kenneth Mason Publications Ltd. However with suchdevices the large volume of oxygen gas is still directly mixed into thegas flow, and there is still a region in the gas stream where theoxygen-gas mixture can be explosive, owing to pockets of not fully mixedgases.

By the use of microchannel apparatus, mixing of oxidant and hydrocarbonoccurs in one or more individual process microchannels. Preferably theoxidant and the hydrocarbon are in the gas phase. The oxidant stream andthe hydrocarbon stream are desirably added via separate feed lines tocommon process microchannels. Since there exists a large number ofprocess microchannels within a microchannel apparatus, the oxidant feedand the hydrocarbon feed is split up into multiple small volumes for themixing to occur in individual process microchannels. This ensures a highefficiency of mixing and where the feeds are gases minimizes the volumeof gas that is in the explosive region. Inside the microchannels,explosion cannot take place as heat is immediately dissipated and theflame quenched making the apparatus intrinsically safe. When fullymixed, the mixture from each process microchannel will converge into onestream either within the microchannel apparatus or via a header into anexternal exit line, and a fully mixed stream is provided with minimalexplosive risk.

Having regard to FIG. 2 herewith, it is possible, for example, for oneof the two feed streams, preferably the hydrocarbon stream, to enter onemicrochannel section 240 via process microchannels 260 and/or 220, andfor this feed to be led via intermediate section 440 into a secondsection 340 wherein the other of the two feeds, preferably the oxidant,is introduced via second feed channel 360. Mixing of the two feeds canthen occur in the microchannel 230 to which the second feed is directedvia orifices 380. If necessary for the feed components involved or toprovide enhanced safety, the microchannel apparatus may also compriseheat exchange channels, which may themselves be microchannels, throughwhich a cooling medium can be run.

In the present invention, the oxidant is most preferably oxygen gas. Ahydrocarbon or hydrocarbon material herein may be any organic compoundthat contains hydrogen and carbon; other elements such as oxygen mayalso be present. In this aspect of the present invention a hydrocarbonmaterial may be one or more of hydrocarbons such as C₁₋₁₀ hydrocarbons,for example methane, ethylene, ethane, propylene, propane and butane;oxides such as C₂₋₁₀ alkylene oxides, for example ethylene oxide;glycols such as C₂₋₁₀ alkylene glycols for example mono-, di- ortri-ethylene glycol; and C₁₋₁₀ organic acids such as acetic acid. Thus,the process of the present invention may for example be utilized in thecatalytic partial oxidation of ethylene to ethylene oxide or to vinylacetate.

The present invention most suitably provides a process for thepreparation of ethylene oxide, which comprises introducing a source ofoxygen into one or more process microchannels of a microchannelapparatus and introducing into the same process microchannels a sourceof ethylene, allowing mixing to take place to form a gaseous productmixture, and conveying the gaseous product mixture to a reaction regionwherein reaction to ethylene oxide can occur. Preferably the source ofethylene comprises a mixture of ethylene and one or more compoundsselected from methane, ethane, oxygen, argon, carbon dioxide andnitrogen. The process of the present invention is most preferablyutilized where the source of oxygen is oxygen gas having a purity in therange of from 95 to 99.99% by volume; however the oxygen source may alsobe air or oxygen gas of a lower purity, for example of 85% by volume andabove, and thus preferably the oxygen source is a gas having an oxygencontent in the range of from 15 to 99.99% by volume.

In this aspect of the present invention, the gases are mixed on a‘microlevel’, i.e. on a very small scale, within process microchannelsof the microchannel apparatus. Initially after intermingling of bothfeeds there will of course be pockets of oxygen-rich and oxygen-poormixtures, however the splitting up and recombination of the oxygen flowin the process microchannels and, where present, via the microchannelorifices, will establish an average oxygen concentration below explosionlimits. As the gas mixture progresses through the microchannelapparatus, these pockets will disappear and the gases will becomewell-mixed on a microlevel.

In an EO manufacturing plant, it is most useful to locate themicrochannel apparatus in the recycle gas loop at the same locationwhere conventional mixing apparatus is utilized i.e. prior to thereactor. However it is possible to locate the microchannel apparatus atany location in the recycle gas loop. In certain locations theconditions of the gas, for example its composition, pressure and/ortemperature, could cause even the final well-mixed gas to be in theexplosive region; in such circumstances it may be necessary to adjustthe conditions to allow the process of the invention to be used, forexample to reduce the temperature of the recycle gas stream. A feed linesuitably runs from the ethylene source into the apparatus, and aseparate feed line is provided from the oxygen source. The generalprocess conditions that may apply for the mixing operation are suitablya pressure in the range of from 1000 to 3500 kPa, and a temperature inthe range of from ambient (20° C.) to 250° C.

The process of the present invention provides enhanced mixing in a rapidtimescale, and indeed is able to provide a fully mixed product in ashorter timescale than previous proposals, particularly for the mixingof gases having an explosive potential.

Thus the use of the microchannel apparatus provides the advantage ofrapidly splitting up the feed gases and mixing small volumes together ata much faster rate than is achievable by the prior ring mixing devices.The length of time that any mixture may exist in the explosive region issignificantly reduced and the finally fully mixed gas stream is achievedmuch quicker.

The size of the microchannels themselves additionally ensures that themixing apparatus functions as a flame arrester. For any gas or gasmixture there is a characteristic flame quench diameter; this is thediameter of pipe or container in which any flame would be quenched. Byselection of the appropriate microchannel diameter it can be ensuredthat any starting combustion reaction can be immediately quenched. Thusthe physical nature of a microchannel apparatus additionally may provideintrinsic safety for the mixing operation—this is not at all possiblewith current mixing systems. Where the microchannel apparatusadditionally includes heat exchange channels, the safety advantages arefurther enhanced.

In a process of the present invention, it is thus preferred to use amicrochannel apparatus having one or more, and preferably all, processmicrochannels having an internal dimension of height and/or width of atmost 5 mm, most preferably at most 2 mm, and especially at most 1.5 mm.Said internal dimension is preferably at least 0.1 mm, most preferablyat least 0.5 mm, and especially at least 0.5 mm.

Another process operation that presents an explosion risk, particularlyin an ethylene oxide plant, is the handling of ethylene oxide itself.Ethylene oxide (EO) is an unstable and very reactive component. Inequipment that contains EO vapor, several reactions can occur which areexothermic. Where the heat of reaction is not removed fast enough, thetemperature in the equipment can increase rapidly and, if unchecked, canlead to explosive decomposition reactions of the EO vapor. Whereadditional substances are present then explosive reactions can occur atlower temperatures than for pure ethylene oxide. Even EO liquid undercertain circumstances can be dangerous.

In a commercial ethylene oxide production plant, the sections for whichthis is of most concern are the EO concentrator and the EO purificationsections. The EO concentrator is often also called the EO stripper. BothEO concentrator and the EO purification sections utilize a distillationcolumn, to separate EO from water, which may be equipped with acondenser and an EO condensate collection vessel. In the latter,stagnant, liquid EO exists possibly in conjunction with water. In orderto reduce the chance of explosive decomposition reactions, whether in adistillation column or in an EO condensate collection vessel, the topsection plus overhead system of an EO concentrator column and of an EOpurification column are conventionally operated under nitrogen pressure,which increases the operating pressure by at least a factor of 1.7. Thepressure can also be generated by use of a gas other than nitrogen,which may be selected from one or more of carbon dioxide, methane and aprocess gas such as a light ends gas. Usually, however, nitrogen isused. It would be most desirable to be able to operate these columnswithout the need for pressurization in the top section, yet still have alow explosion risk.

The use of microchannel apparatus has the advantage of being able tocool an ethylene oxide-containing mixture very efficiently, thusminimizing the likelihood of explosive decomposition reactions. Sincethere exist a large number of process microchannels within amicrochannel apparatus, and because of the dimensions of the processmicrochannels, the EO-containing feed is split up into multiple smallvolumes. A heat transfer medium is run through heat exchange channels ofthe apparatus to ensure a rapid heat flux from EO to heat transfermedium. These features ensure a high efficiency of heat transfer andminimize the volume of gas that can be in the explosive region.Furthermore the nature of the process microchannels means that theapparatus can act as a flame arrester and provide an intrinsically safecondensation system for EO-containing gases. In this aspect of thepresent invention, it is thus also preferred to use a microchannelapparatus having one or more, and preferably all, process microchannelshaving an internal dimension of height and/or width of at most 5 mm,most preferably at most 2 mm, and especially at most 1.5 mm. Saidinternal dimension is preferably at least 0.1 mm, most preferably atleast 0.5 mm, and especially at least 0.5 mm.

In the process of the present invention, the gaseous mixture comprisingethylene oxide may contain in the range of from 50 to 100% by weight ofEO. The gaseous mixture may also comprise one or more of the following,in gaseous form: water; carbon dioxide; argon; nitrogen; oxygen;ethylene glycols such as mono-ethylene glycol, di-ethylene glycol andtri-ethylene glycol; aldehydes such as acetaldehyde, and formaldehyde;hydrocarbons such as ethylene, methane, and ethane; and hydrocarbonmaterials and/or chlorinated hydrocarbon impurities such as alcohols,acids, acetals, cyclic acetals, ethers, cyclic ethers, esters such as1,4-di-oxane, 1,4,7-tri-oxane, 1,3-di-oxolane, 2-methyl-1,3-di-oxolane,2-chloro-methyl-1,3-di-oxolane, 2-chloro-ethanol,2-chloro-methyl-1,3-di-oxolane, glyoxal, oxalic acid, glycolic acid,glyoxilic acid, lactic acid, acetic acid, formic acid and their esters.

The use of microchannel apparatus can provide a much larger heattransfer than conventional shell and tube heat exchangers, and is a muchsmaller item of equipment. Thus a CAPEX improvement is given by thecombination of smaller condensation equipment as well as by the removalof reflux drums. The apparatus also has the potential to reduce the needfor excess pressurization of the upper sections of these columns. TheOPEX may also be improved by any reduced pressurization in the topsection of these EO distillation columns. Where the pressure can bereduced then there is additional significant advantage, particularly inan EO stripper or concentrator, in that a lower temperature steam can beused to heat the column and the amount of glycol by-product can bereduced. Furthermore the microchannel apparatus acts as a flame arresterand provides an intrinsically safe EO condensation system.

Thus the present invention preferably provides a process for theconcentration or purification of ethylene oxide, which comprises

a) absorbing ethylene oxide from a first gaseous stream with a suitableabsorbent,

b) desorption of the ethylene oxide in a distillation unit to form asecond gaseous stream containing ethylene oxide, and

c) recovering ethylene oxide,

wherein the second gaseous stream of step b), is condensed in one ormore process microchannels of a microchannel apparatus.

Suitable absorbents that can absorb ethylene oxide are documented inliterature and include water (see Research Disclosure No. 465117, idem);ethylene carbonate (see U.S. Pat. No. 4,221,727 and EP-A-776890);propylene carbonate (EP-A-705826); aqueous ethylene glycol solutionshaving a glycol content up to 40% and antifoam additive content of up to500 ppm (U.S. Pat. No. 4,875,909 and GB-A-1435848); methanol (U.S. Pat.No. 3,948,621); organic liquid solvents (U.S. Pat. No. 4,249,917); andliquid hydrocarbons such as methane, ethane and/or ethylene in liquidform (U.S. Pat. No. 3,644,432). However, most commonly water or anaqueous solution is utilized and is preferred in the process of thepresent invention.

In step a) absorption of ethylene oxide with water or an aqueoussolution creates an aqueous solution of ethylene oxide. In step b) theethylene oxide is then desorbed by dewatering in a distillation unit.

A distillation unit may comprise one or more distillation columns. Mostsuitably a maximum of five distillation columns are utilized in serieswithin a unit forming a ‘distillation train’. Preferably a distillationunit comprises from one to three distillation columns, most preferablyonly one distillation column. Where a single column is utilized in stepb) the second gaseous stream is obtained in the upper section of thecolumn, and an aqueous product is given in the bottom section. In adistillation train of columns equivalent product streams are obtained atappropriate points, as would be well known to the skilled person in theart.

The term ‘dewatering’ herein should be understood to mean the removal ofwater.

In a preferred embodiment, step a) is the absorption of ethylene oxidein an aqueous solution to produce a stream in which water is enrichedwith EO and step b) is performed in an EO stripper or concentrator,which is a single distillation column. While the EO is stripped orconcentrated from the aqueous feed stream, the product drawn off fromthe upper section, and preferably drawn off at the very top, of thedistillation column is still a mixture of ethylene oxide and water. Thisgaseous mixture product is condensed in a microchannel apparatus and theresulting EO-containing stream can be utilized for the production ofother chemicals such as 1,2-diols, 1,2-diol ethers, 1,2-carbonates oralkanol amines by processes known in the art, or it can be furtherpurified to yield a high purity EO. A portion of said resultingEO-containing stream may be recycled to the EO concentrator column, anda bleed of gases, such as methane, CO₂ and ethylene, can be drawn off byprocedures well known to those skilled in this art. In this embodiment,the first gaseous stream is an EO-containing product stream of a reactorin which ethylene and oxygen are reacted to form ethylene oxide.Preferably the first gaseous stream comprises EO in the range of from 2to 50% by weight, more preferably from 2 to 10% by weight, andespecially from 4 to 6% by weight. The aqueous solution of step a)primarily comprises water in an amount from 50 to 100% by weight. It ispossible that in the range of from 0.1 to 20, e.g. 2 to 10, % by weightof said aqueous solution is a glycol, mostly being mono-ethylene glycol.In such solutions an anti-foam additive is not required but may beutilized if desired.

In an alternative preferred embodiment step b) may be performed severalstages downstream of step a) and in the EO purification section of an EOproduction process, in which case the second gaseous stream will containpredominantly EO, with trace amounts of impurities. Thus less than10,000 ppm, i.e. for example from 1 ppm to 10,000 ppm, of othercompounds may also be present. Such compounds may comprise for examplewater, carbon dioxide, argon, nitrogen, oxygen, aldehydes, such asacetaldehyde, and formaldehyde, and, as above, other hydrocarbons,alcohols, acids, acetals, cyclic acetals, ethers, cyclic ethers, andesters. In this embodiment, the second gaseous stream is purifiedethylene oxide which may be drawn off at any point in the upper sectionof the distillation column, thus it may be drawn off directly in gaseousform via a top draw-off, above the upper plate or internal packing, orvia a gaseous or liquid side draw-off below the upper tray or upperlevel of packing.

In both embodiments, it is preferred that the second gaseous streamcomprises 50% by weight or more of EO.

In a further aspect of the present invention, apparatus is provided forthe concentration or purification of ethylene oxide from a mixture ofethylene oxide and water, which is a distillation column connected to amicrochannel apparatus. Advantageously, the microchannel apparatus ispositioned inside the shell of the distillation column at a point abovethe uppermost distillation tray or packing material.

By incorporating microchannel apparatus inside the distillation columnit is possible to provide integral reflux within the column whichsignificantly improves process safety. In a commercial EO productionplant, such use, in accordance with present invention, of an integratedmicrochannel apparatus to cool EO gases within a distillation columnallows cooling, by condensation, to occur without the need of anexternal condensate collection vessel. The presence of stagnant EO istherefore avoided and the likelihood of explosion is minimized.

The operation of the process of the present invention can be described,for example, with reference to FIG. 1 herewith.

The gaseous mixture comprising ethylene oxide, which preferably is agaseous stream forming the top stream of an EO stripper or of an EOpurification column, enters header 102 and is split into multipleportions to progress through the reactor via a plurality of processmicrochannels 104. Coolant is fed into the apparatus via heat exchangeheader 110 and flows through the apparatus cross-currently (as shown inFIG. 1) or co- or counter-currently, via heat exchange channels to thefooter 112.

When the microchannel apparatus is sited within a distillation column,it is most suitably sited in the centre of the column and may extendacross the full diameter of the column, being affixed directly to thecolumn walls, or across the diameter only in part. In the latter casethe apparatus may be placed on beams extending from the inner columnwalls or may be suspended by arms extending from the inner column walls,provided that the beams or arms do not restrict the gas and liquid flowin the column. The height of the microchannel apparatus suitably also issuch as to not interfere with the normal operation of the distillationcolumn; and the length of the process microchannels most suitably is inthe range of from 5 to 100 cm.

In all cases it is important that gas flow in the distillation columncan circulate to the top of the column, either around the outside of themicrochannel apparatus or through channels or holes in the apparatus.The microchannel apparatus is so sited that the second gaseous streamenters the apparatus via a header at the top of the apparatus as inFIG. 1. The gaseous stream condenses within the process microchannelsand liquid ethylene oxide runs through the process microchannels andcollects in an exit header, or other collection unit, at or under thebottom of the apparatus, and can be withdrawn from the column. Thecondensation causes the gaseous stream automatically to be drawn intothe process microchannels. Coolants can be routed into the apparatus andmay for example be water or other coolant material that takes up heatcreated by the condensation.

The general process conditions that may apply for the use ofmicrochannel apparatus in an EO condensation process of the inventionare suitably a temperature in the range of from ambient (20° C.) to 100°C., for example 30 to 50° C., and a pressure in the range of from 100 to1,000 kPa, for example 200 to 400 kPa.

Volatile contaminants are often produced by industrial chemicalprocesses. Such contaminants are often vented to the atmosphere but withincreasing environmental legislation, smaller amounts of suchcontaminants are permitted to be vented from commercial manufacturingplants.

One such area in which contamination in vent or waste gas can occur isin the production of ethylene oxide. The residual gases that remainafter recovery of the bulk ethylene oxide product, are recycled to theethylene oxidation reactor. A side stream, part or all of the recyclegas, is usually scrubbed with an aqueous CO₂ absorbent for removal ofexcess CO₂ which is subsequently stripped from the absorbent and may bevented, or preferably is recovered for use or sale as a by-product. Aproblem arises particularly in manufacturing plants of large capacity inthat during scrubbing of the recycle gas side stream, small amounts ofhydrocarbon are dissolved and/or entrained in the CO₂ absorbent and needto be removed to avoid contamination of the carbon dioxide.

Various systems have been proposed for the removal of volatilecontaminants from vent gases. Such contaminants may be organichydrocarbons, such as ethylene, methane, ethylene oxide, andhalogen-containing compounds. Where the contaminant is a volatileorganic compound, current removal processes utilize thermal or catalyticdecomposition, preferably combustion.

In many industrial processes the vent gases are cleaned of theseimpurities in an oxidizer by total combustion in a packed bed reactor,either thermally or catalytically if the reactor contains a catalyst. Insome instances, such a reactor is combined with a heat exchanger inorder to recover the combustion heat generated. Such combustion, orincineration, can for example occur within a catalytic incineratorwhereby one or more catalyst beds are heated to high temperatures (inthe range of from approximately 300° C. to 800° C.; typically 500° C.)and operate at atmospheric pressure. In the thermal combustion systemsthe temperatures may be in the range of from 700 to 1000° C. and alsooperate at atmospheric pressure. Various heat exchange mechanisms aretherefore also incorporated to minimize energy loss and improveefficiency.

A more sophisticated system is the reverse flow reactor. Reverse-flowreactors are well known in the art. The general principle of suchreactors has been described in detail in “Reverse-Flow Operation inFixed Bed Catalytic Reactors”, Cata. Rev.-Sci. Eng., 28(1), 1-68 (1996).

Reverse-flow reactors have been employed in a number of differentlarge-scale heterogeneous processes, such as catalytic incineration ofvolatile organic contaminants, the hydrogen sulphide oxidation bysulphur dioxide, Fischer-Tropsch synthesis over ruthenium and cobaltcatalysts, the selective reduction of carbon monoxide and/or nitricoxides in flue gases, and similar processes, as described in U.S. Pat.No. 6,261,093, CA-A-1,165,264, U.S. Pat. No. 5,753,197, and U.S. Pat.No. 5,589,142.

A simple reverse-flow reactor for catalytic reactions on a fixedcatalyst bed consists of a reactor vessel comprising at least onecatalyst bed and optionally, one or more beds of refractory packings,often referred to as inerts to hold the catalyst bed in place which alsomay provide for additional heat capacity, together with the necessaryline-up and switching valves that allow oscillation of the flowdirection of a fluid or gaseous reaction medium between the respectivereactor in- or out-let.

A reverse-flow reactor has the disadvantage that the system containsswitching valves that are subject to mechanical stresses causingmechanical failure.

The present invention utilizes microchannel apparatus to combustvolatile contaminants in a vent gas or other gas stream; this is aneffective means of removing such contaminants and additionally allowseffective heat exchange to occur in the same apparatus as combustion,thereby combining the two processes in one piece of equipment resultingpotentially in a lower CAPEX. In particular, against a reverse-flowsystem, the complex switching mechanism is avoided and the processbecomes simpler and more reliable.

Thus, using a microchannel apparatus as an oxidizer is simpler, easierto operate and potentially less expensive than prior proposals. Theapparatus will combine a high heat integration with a high efficiency ofcombustion which is very important to remove low, ppm, amounts ofcontaminants. In the prior proposals, even with the sophisticatedreverse flow reactor, leakage occurs, via the switching valves orthrough by-pass mechanisms to avoid overheating, which make the systemsunreliable. A microchannel apparatus enables heat control via othermechanisms than a separate heat exchanger or by-pass systems, and doesnot utilize switching valves.

The present invention accordingly provides a process for the removal ofcombustible volatile contaminant materials from a first process stream,which comprises

a) flowing a first process stream through a first set of processmicrochannels in a microchannel apparatus,

b) heating said first process stream to the combustion temperature ofthe volatile contaminant materials and combusting the volatile materialsto form a hot cleaned stream, which may also contain combustionproducts,

c) conducting the hot cleaned stream through heat exchange channels,which may preferably be a second set of process microchannels, which arein thermal contact with said first set of microchannels, andsubsequently

d) recovering a cooled, cleaned process stream.

The volatile contaminant materials may be any of the following organichydrocarbons: ethane, ethylene, methane, ethylene oxide, andhalogen-containing compounds such as organic chlorides. Suchcontaminants may be present in an amount in the range of from 0.05 to 1%by weight of the first process stream, for example 0.05 to 0.5% byweight.

The combustion or incineration of the volatile contaminants occurswithin a first set of process microchannels within a microchannelapparatus and yields combustion products of water and carbon dioxide.These may be carried with the treated stream out of the microchannelapparatus to be removed with the rest of the gas stream. These heatedgases are conducted to a first set of heat exchange channels which arein thermal relationship with said first microchannel set. In this waythe heated gases heat the first process stream to combustiontemperature. To allow for start-up and for thermal losses that mayoccur, an additional heating device may be necessary to heat the firstprocess stream at the start of operation of the process, and to ensurethe necessary heat to reach combustion temperature within the first setof microchannels. Such an additional heating device can be readilyincorporated into the microchannel apparatus by means of a simple burneror as a second set of heat exchange channels, for example. It isexpected that the microchannel apparatus will lead to less thermal lossfrom the hot cleaned stream, and that such ancillary heating means willbe less required than in prior proposals.

The first set of heat exchange channels are preferably adjacent to thefirst set in the form of a second set of microchannels. The two sets of(micro) channels can be so configured as to allow co-current flow,counter-current flow, or cross-current flow for the two process streams.Most preferred is a configuration that establishes counter-current orcross-current flow, and especially counter-current flow. While theapparatus may be set up so that the hot cleaned stream may exit themicrochannel apparatus and re-enter in order to be aligned in thermalcontact with the first process stream, for reasons of thermal economy itis preferred for the hot cleaned stream to remain in the microchannelapparatus until the heat exchange with the first process stream hasoccurred. Thus preferably the first process stream will flow through thefirst set of microchannels and then be led to the first set of heatexchange channels which are positioned adjacent to the full length ofthe first set of microchannels. The cooled, cleaned process stream inthis embodiment will usually exit the apparatus close to the point atwhich the first process stream enters. The exit of from the microchannelreactor may however be at any suitable point, and may be at the oppositeend of the apparatus to the inlet point in certain embodiments.

If the combustion provides excess heat than is needed for the heating ofthe first process stream, for example because the first process streamis already heated before treatment, or the combustion reaction needs tobe controlled thermally, then additionally a second set of heat exchangechannels may be present in the microchannel apparatus which can removeexcess heat from the combustion reaction, which heat can be useddirectly, or at another location, for example to produce steam. Saidsecond set of heat exchange channels are preferably also microchannels,and would then form a third set of microchannels. Alternatively, part ofthe hot gases can be bled off.

It is preferred that such a process be utilized for the removal ofvolatile organic hydrocarbons from a carbon dioxide process stream, mostpreferably for the removal of one or more of ethylene, methane, andethylene oxide. The carbon dioxide stream is preferably a CO₂ wastestream from an ethylene oxide production plant. The level of purityachieved means that the cleaned CO₂ may be sold as a commercial product.

However, the process of the invention may be utilized in any situationwhere currently an oxidizer or incinerator is utilized to removevolatile organic impurities, such as to treat any vent gas from acommercial petrochemicals plant or off-gas from a tankfarm; and indeedfor the cleaning-up of any gas streams that have from 1 ppm to 10% byvolume of volatile organic hydrocarbon impurity.

The microchannel apparatus may be adapted to allow catalytic combustionor incineration of the volatile contaminant materials. As previouslymentioned, a catalyst can be incorporated into the process microchannelsin a number of suitable ways. The catalyst components most suited tocatalytic combustion are well known to those in the art. A suitablecatalyst component comprises, as the catalytically effective component,a metal or cationic metal component selected from platinum, palladium,rhodium, rhenium, nickel, cobalt and manganese; a refractory oxidecarrier such as alumina may also be present but is not required. Thecatalyst may be incorporated in solid form as a packing within themicrochannels or via a wash-coating onto the walls of one or more of theprocess microchannels, most suitably of the first set of processmicrochannels.

The process of the invention is carried out at the conventionaltemperatures and pressures noted above for thermal and catalyticincinerators.

The thermal conversion of ethylene oxide and water to ethylene glycol iswell known and commercially practiced world-wide, see for example thedescription in Ullmann's Encyclopedia of Industrial Chemistry, Volume A10, pages 104 & 105. The thermal process requires a high molar excess ofwater, as much as a 20-fold molar excess, to yield the most desiredproduct of mono-ethylene glycol. Catalytic conversions that areselective to mono-ethylene glycol and that do not require such highexcess of water are also of interest. Catalytic processes for convertingalkylene oxides directly to alkylene glycols in general have beeninvestigated and catalysts capable of promoting a higher selectivity tomonoalkylene glycol product at reduced water levels are known, (e.g.EP-A-015649, EP-A-0160330, WO 95/20559 and U.S. Pat. No. 6,124,508).

All of these conversion reactions are highly exothermic.

The present invention provides a process for the preparation of analkylene glycol by the reaction of a corresponding alkylene oxide andwater, which process comprises

a) flowing the alkylene oxide and water through a microchannel reactor,wherein the oxide and water undergo an exothermic reaction to form thecorresponding alkylene glycol,

b) transferring heat from the microchannel reactor to a heat transfermedium, and

c) recovering the alkylene glycol product from the microchannel reactor.

Utilizing a microchannel reactor provides the advantages of a highremoval rate of the heat of reaction, and a much greater temperaturecontrol of the full conversion process.

The microchannel reactor can also incorporate a catalyst system thatpermits the reduction of the high water excess. Such a catalyst systemmay be a homogeneous catalyst that is mixed with the reactants eitherbefore entry to the reactor or within the reactor, or it may be aheterogeneous system present as a solid catalyst or as a coating,preferably a wash-coating, on the walls of one or more, and desirablyall, of the process microchannels present in the reactor.

Catalysts that may be employed in the present process are known in theart. Suitable catalysts are acid catalysts and basic catalysts.

Homogeneous catalysts include acidic catalysts which are liquid underthe conditions of the reaction. Suitably such catalysts are mineralacids, such as sulphuric acid and phosphoric acid, and such catalysts asknown from JP-A-56-092228.

Homogeneous metalate catalysts are also very suitable; such catalystscomprise a salt selected from vanadates, molybdates and tungstates.Suitable examples are described in U.S. Pat. No. 4,551,566, EP-A-156447,and EP-A-156448.

Less preferred are heterogeneous catalysts. Ones that may be mentionedare acidic catalysts such as strongly acidic ion exchange resins, suchas those comprising sulphonic acid groups on a styrene/divinylbenzenecopolymer matrix, and silicas and oxides of metals selected from Groups3 to 6 of the Periodic Table of Elements, for example zirconium oxideand titanium oxide. As basic catalysts there may be mentioned thosecomprising an ion exchange resin (IER) as a solid support, in particularthe strongly basic (anionic) IER's wherein the basic groups arequaternary ammonium or quaternary phosphonium on astyrene/divinylbenzene copolymer matrix. Also suitable as heterogeneouscatalysts are metalates, such as vanadates, molybdates and tungstates,contained on a solid support such as an ion exchange resin or ahydrotalcite clay as described in EP-A-156449 and EP-A-318099.

Suitable ion exchange resins utilized may be based on vinylpyridine,polysiloxanes. Other solid supports having electropositive complexingsites of an inorganic nature may also be utilized, such as carbon,silica, silica-alumina, zeolites, glass and clays such as hydrotalcite.Further, immobilized complexing macrocycles such as crown ethers, etc.can be used as well as a solid support.

Such heterogeneous catalyst may be based on a strongly basic quaternaryammonium resin or a quaternary phosphonium resin, for example an anionexchange resin comprising a trimethylbenzyl ammonium group. Examples ofcommercially available anion exchange resins on which the catalyst maybe based include LEWATIT M 500 WS (LEWATIT is a trademark), DUOLITE A368 (DUOLITE is a trademark) and AMBERJET 4200 (AMBERJET is atrademark), DOWEX MSA-1 (DOWEX is a trademark), MARATHON-A andMARATHON-MSA (MARATHON is a trademark) (all based on polystyrene resins,cross-linked with divinyl benzene) and Reillex HPQ (based on apolyvinylpyridine resin, cross-linked with divinyl benzene).

The anion exchange resin in the fixed bed of solid catalyst may comprisemore than one anion which may be selected from the group of bicarbonate,bisulfite, metalate and carboxylate anions.

When the anion is a carboxylate anion, it maybe a polycarboxylic acidanion having in its chain molecule one or more carboxyl groups and oneor more carboxylate groups, the individual carboxyl and/or carboxylategroups being separated from each other in the chain molecule by aseparating group consisting of at least one atom. The polycarboxylicacid anion is suitably a citric acid derivative, more preferably amono-anion of citric acid.

A suitable solid catalyst is a catalyst based on a quaternary ammoniumresin, preferably a resin comprising a trimethylbenzyl ammonium group,and wherein the anion is a bicarbonate anion.

The alkylene oxides used as starting materials in the process of thepresent invention, have their conventional definition, i.e. they arecompounds having a vicinal oxide (epoxy) group in their molecules.Preferred alkylene oxides are alkylene oxides of the general formula:—

wherein each of R¹ to R⁴ independently represents a hydrogen atom or anoptionally substituted alkyl group having from 1 to 6 carbon atoms. Anyalkyl group, represented by R¹, R², R³ and/or R⁴, preferably has from 1to 3 carbon atoms. Optional substituents on the alkyl groups includehydroxy groups. Preferably, R¹, R², and R³ represent hydrogen atoms andR⁴ represents a non-substituted C₁-C₃-alkyl group and, more preferably,R¹, R², R³ and R⁴ all represent hydrogen atoms.

Examples of alkylene oxides which may conveniently be employed includeethylene oxide, propylene oxide, 1,2-epoxybutane, 2,3-epoxybutane andglycidol. The alkylene oxide is preferably ethylene oxide or propyleneoxide; ethylene glycol and propylene glycol being alkylene glycols ofparticular commercial importance. Most preferably the alkylene oxide ofthe present invention is ethylene oxide or propylene oxide and thealkylene glycol is ethylene glycol or propylene glycol.

When the conversion is a thermal conversion, the temperature may be inthe range of from 100 to 300° C., in particular from 150 to 250° C. Whenthe conversion is a catalytic conversion, the temperature may be in therange of from 30 to 200° C., in particular from 50 to 150° C. The molarratio of water to the alkylene oxide may be in the range of from 5 to50, in particular from 10 to 30. The pressure may be in the range offrom 500 to 3500 kPa, as measured at the second feed channel, describedhereinbefore.

In certain embodiments of the present invention it may be beneficial toadd carbon dioxide to the (catalytic) reactor to establish advantageousconditions for the hydrolysis. Such carbon dioxide may conveniently beadded directly to the reactor or it may be added to the alkylene oxidefeed. If carbon dioxide is to be added, the amount of carbon dioxideadded may be varied to obtain optimum performance in relation to otherreaction parameters, in particular the type of catalyst employed.However the amount added will preferably be less than 0.1% wt, morepreferably less than 0.01% wt, based on a total amount of reactants inthe second reactor.

With reference to FIG. 2, as an example, alkylene oxide may be fed intofirst section 240 via feed channels 260 and/or 220, and water may beco-fed through the same channels or fed into the microchannel system viafeed channel 360 of second section 340. In a specific embodiment whenthe oxide is fed through channel 240, then, water may be fed throughchannels 220 and mixed with the oxide in the microchannels. To removeheat evolved during the reaction, coolant may flow via heat exchangechannels 250 and/or 350 depending on the site of reaction and thechannel through which the water feed is fed. If alkylene oxide and waterare co-fed to the first section, then where catalyst is present, anyadditional component useful for the reaction, such as carbon dioxide,may be fed to the reactants via the second section 340.

The use of a microchannel reactor permits a greater control of theexothermic reaction than has hitherto been possible which reduces theneed for excess volumes of water to act as a heat sink.

The hydration of ethylene oxide to mono-ethylene glycol (MEG) isnormally carried out in the liquid phase in, for example, a pipe or tubereactor. As noted above previously proposals to use catalysts in suchconversions have been made. Additionally it has been proposed to reactEO and water in the vapor phase since this can be beneficial in terms ofprocess integration and separation. Regarding the latter in particularthe removal of MEG from a gas stream is possibly easier than from adilute aqueous stream as in conventional plants.

Heterogeneous hydrolysis catalysts can also be utilized in vapor phasehydration, where mono-ethylene glycol will be formed as the mainproduct. However inevitably the EO present will also react with theformed glycols to form higher molecular weight glycols, for example EOwith mono-ethylene glycol will form di-ethylene glycol, with di-ethyleneglycol EO will form tri-ethylene glycol, and so forth. The major problemwith the use of heterogeneous catalysts for vapor phase reactions isthat the higher glycols have a high boiling point and thus are liquid atthe typical reaction temperature and pressure applied. Thus the catalystsurface will be covered with glycols quickly growing in molecular weightleading to deactivation of the catalyst. MEG may also be trapped asliquid on the catalyst surface. Also the reaction of EO with glycols onthe surface of the catalyst will result in a reduced selectivity of EOto mono-ethylene glycol product.

The use of certain highly selective heterogeneous catalysts in the vaporphase hydration of ethylene oxide has been proposed in the literature,most recently in EP-A-318099 and EP-A-529726 which describe the use ofspecific hydrotalcites, which are anionic clays, both for vapor andliquid phase hydration.

However even with a high degree of selectivity to mono-ethylene glycol,the problem of deactivation by deposition of other glycols produced asby-products in vapor phase hydration will still exist.

In the present invention it is proposed to operate a gas phase reactorin a ‘swing’ mode. In mode 1, the reaction mode, the temperature andpressure are optimized to achieve the desired production ofmono-ethylene glycol. A heterogeneous catalyst which is highly selectiveto the production of MEG is preferably used. Preferably the temperatureis maintained in the range of from 200 to 350° C., most suitably 200 to275° C., and the pressure in the range of from 100 to 1000 kPa. Suitablythis process is performed without excessive amounts of water. The amountof water is preferably in the range of from 1 to 35 moles per mole ofalkylene oxide, more preferably from 1 to 20 moles, most preferably from1 to 10 moles, per mole of alkylene oxide.

The heterogeneous catalysts preferred for use in such a process arebased on support materials selected from members of the family of clays;aluminas, for example α- and γ-alumina; zirconias; silicas; andhydrotalcites (anionic clays).

Such support materials suitably have a metal component, for example ametal ion or a metal oxide deposited thereon to enhance activity and/orselectivity, but can be utilized above. Any metal or metal component canbe incorporated into the catalyst. Most suitably such a metal componentmay be selected from one or more metals of Groups IA, IIA, IIIA, IVA,VA, VIA, VIIA, VIIIA, IB, IIB, and IIIB of the Periodic Table (using theIUPAC notation). Very suitable metals include sodium, cesium,molybdenum, nickel, cobalt, zinc, aluminum, lanthanum, rhenium,tungsten, and vanadium.

Suitable catalyst components may also include anionic groups such ashydroxide ions, carbonate ions, sulphate ions and phosphate ions.

Where the support material is a hydrotalcite, such materials are anionicclays and consist of positively charged layers of oxides and/orhydroxides, for example in conjunction with a mixture of Mg²⁺ and Al³⁺cations, separated by a layer containing water and charge compensatinganions, for examples hydroxides or carbonates.

Examples of suitable catalyst systems are: MoO₄/ZrO_(x)(OH)_(4-2x);Cs/α-Al₂O₃; Co/Mo/α-Al₂O₃; Zn/Al/CO₃ hydrotalcite; Co/Mo/SiO₂;Mo/Co/Zn/Al hydrotalcite; hydrotalcite/Na-citrate;Co/Zn/Al-hydrotalcite; Mo—Co/Zn/Al-hydrotalcite; SiO₂ granules; 12 wt %La/α-Al₂O₃; SO₄/ZrO_(x)(OH)_(4-2x); SO₄/ZrO₂; ZrO_(x)(OH)_(4-2x); ZrO₂;PO₄/ZrO_(x)(OH)₄₋₂; PO₄/ZrO₂; ReO₄/ZrO_(x)(OH)_(4-2x); ReO₄/ZrO₂;WO₄/ZrO_(x)(OH)_(4-2x); WO₄/ZrO₂; MoO₄/ZrO_(x)(OH)_(4-2x); MoO₄/ZrO₂;Ni/V hydrotalcite; Ni/V hydrotalcite-coated Al/5 Mg; α-Al₂O₃; Co/α-Al₂O₃dried; Co/α-Al₂O₃ calcined; Cs/α-Al₂O₃ dried; Cs/α-Al₂O₃ calcined;Co/Mo/α-Al₂O₃ dried; Co/Mo/α-Al₂O₃ calcined; ZnAlCO₃ hydrotalcite; andCoMoSiO₂. In the preceding list x, where it appears, is a number from 0to 2.

Such catalysts are either available commercially or may be easilyprepared by techniques well known to the person skilled in the art.

Hydrotalcite-type catalysts of the type proposed in EP-A-529726 are verysuitable. These are hydrotalcite-type catalysts of the general formulaM_(x)Q_(y)(OH)_(2x+3y−nz)A_(z) ^(n−)·aH₂Owherein M is at least one divalent metal cation; Q is at least onetrivalent metal cation; A is at least one component having a valencen-selected from a metalate anion, selected from vanadate (suitablymetavanadate, orthovanadate, pyrovanadate, and hydrogen pyrovanadate),tungstate, niobate, tantalite and perrhenate, and a large organic anionspacer; and a is a positive number. M, Q and A are present such that x/yis greater than or equal to 1, z>0, and 2x+3y−nz is a positive number.The composition has a layered structure where A is located in anionicsites of the composition.

In catalysts of the above general formula in which A is a large organicanion spacer, the selectivity to MEG is increased. Therefore preferablyA is a large organic spacer and may be any organic acid containing fromone to 20 carbon atoms, provided its steric bulk is large. Such organicacid or its alkali salt must be somewhat soluble in a solvent, and mayhave one or more carboxylic acid functional groups, and may have one ormore sulphonic acid functional groups. Large organic anion spacerscontaining carboxylic acid functional groups are preferred, since thesefunctional groups are readily removed by heating. Preferred largeorganic anion spacers include terephthalate, benzoate,cyclohexanecarboxylate, sebacate, glutarate and acetate. Preferably, thelarge organic anion spacer is selected from the group consisting ofterephthalate and benzoate. Terephthalate is the most preferred largeorganic anion spacer. Mixtures of large organic anion spacers may alsobe used.

Preferably x/y is in the range of from 1 to 12, more preferably 1 to 6,and most preferably 1 to 4.

Suitable divalent cations M broadly include elements selected from thetransition elements and Groups IIA, IVA and VA of the Periodic Table(IUPAC version), as well as certain rare earth elements. Specificexamples of divalent metal cations are magnesium, calcium, titanium,vanadium, chromium, manganese, iron, cobalt, nickel, palladium,platinum, copper, zinc, cadmium, mercury, tin, lead and mixturesthereof. Divalent metal cations which are particularly suitable aremagnesium, nickel, cobalt, zinc, calcium, iron, titanium and copper.

Suitable trivalent metal cations Q broadly include elements selectedfrom the transition elements and Groups IIIA and VA of the PeriodicTable as well as certain rare earth elements and actinide elements.Specific examples of trivalent metal cations are aluminum, antimony,titanium, scandium, bismuth, vanadium, yttrium, chromium, iron,manganese, cobalt, ruthenium, nickel, gold, gallium, thallium, cerium,lanthanum and mixtures thereof. Trivalent metal cations which areparticularly suitable are aluminum, iron, chromium, and lanthanum.

The foregoing lists of suitable divalent and trivalent metal cations aremeant to be illustrative but not exclusive. Those skilled in the artwill recognize that other cations can be used, provided that the typesof cations and relative amounts (x/y ratio) result in ahydrotalcite-type catalyst, M is nickel, Q is aluminum, E ismetavanadate and x/y is in the range of 1 to 6. Another preferredhydrotalcite-type catalyst is formed when M is nickel, Q is aluminum, Eis niobate and x/y is in the range of 1 to 6. Hydrotalcite-typematerials in which M is nickel and Q is aluminum are known as takovites.

Such hydrotalcite catalysts may be prepared by the procedures describedin EP-A-529726.

The reactor is changed to mode 2 (step b) once glycols form on thesurface of the catalyst. This can be after reaction time of from 1second to 10 hours, preferably from 10 seconds to 1 hour, depending onthe reaction conditions (temperature and pressure). In mode 2, thedesorption or evaporation mode, the temperature, the pressure, or bothtemperature and pressure, are adjusted to desorb or evaporate theglycols from the surface of the catalyst, while the gas stream is fed toa second reactor. Essentially the temperature has to be increased and/orthe pressure decreased to such conditions as are necessary to cause theglycols to desorb and/or to evaporate. Preferably if temperature aloneis altered then the temperature is changed to be in the range of from250 to 400° C. If the pressure alone is altered then the pressure ispreferably changed to be in the range of from 1 Pa to 500 kPa. If bothtemperature and pressure conditions are altered, then the conditions arepreferably changed to a temperature in the range of from 300 to 350° C.and a pressure in the range of from 1 Pa to 300 kPa. The rate of changeof the temperature and pressure conditions can be optimized to achievemaximum economical benefit.

It may be beneficial also to utilize a sweep gas in mode 2. Such a gasmay be introduced into the reactor, when in mode 2, in order to sweep orcarry the desorbed glycol(s) out of the reactor and onto a separationsection or unit. Suitably such a sweep gas would be an inert gas, suchas steam or preferably nitrogen.

The product MEG may be deposited on the catalyst surface with the otherglycols or preferably remains in the vapor phase. Where the MEG ispredominantly produced and maintained in the vapor phase, the reactormode switching is still necessary to prevent deactivation of thecatalyst by the higher glycols deposited thereon.

The vapor phase mixture of unconverted EO and water and mono-ethyleneglycol product coming out of the reactor zone that is operated in mode1, is suitably led through a downstream zone that is operated at a lowertemperature and/or higher pressure, where the mono-ethylene glycol canbe separated from the gaseous mixture by condensation. If desired, awater/mono-ethylene glycol mixture can be separated by condensation fromthe vapor phase by further lowering the temperature or by furtherincreasing the pressure. This separation or condensation zone may alsobe operated in a ‘swing’ mode. After having condensed mono-ethyleneglycol or mono-ethylene glycol and a part of the water from the reactorproduct vapor stream, this stream may be directed to a second, similarseparator or condensation zone. The condensed product is removed fromthe first zone. During the removal, the temperature or pressure of theseparation zone may, or may not, be changed from the conditions duringcondensation. Where MEG is trapped on the catalyst surface, then it maysimilarly be recovered from the vapor mixture produced in mode 2 byevaporation.

Quick changes in temperature are possible but somewhat difficult in theconventional large vapor phase reactors that are normally used in theprocess industry, particularly those utilizing heterogeneous catalyst,because of the large gas and catalyst volumes, large heat transfermedium volumes, the steel mass (heat sink) and heat transferlimitations. Therefore the reaction, as well as the separation, isadvantageously performed in the process microchannels of one or moremicrochannel reactors, which enables fast and accurate temperature pluspressure change and control. The downstream condensation zone(s) mayalso advantageously be one or more process microchannels of one or morefurther microchannel apparatus.

The present invention accordingly provides a process for the preparationof a mono-alkylene glycol by the reaction of a corresponding alkyleneoxide and water, which process comprises

a) reacting the alkylene oxide and water in a first reactor under afirst set of conditions and in the presence of a catalyst so as toachieve vapor phase conversion to the mono-alkylene glycol,

b) altering the conditions in the first reactor to a second set ofconditions whereby glycols deposited on the surface of the catalyst areremoved,

c) re-establishing the first set of conditions in the first reactor inorder to repeat step a), and

d) recovering the mono-alkylene glycol from a vapor phase mixtureproduced in step a) and/or step b).

In a preferred embodiment the process is operated using two reactorswhereby simultaneously with operating step b), the gaseous alkyleneoxide and water feeds are switched to a second reactor which isoperating under the first set of conditions. When the first set ofconditions are re-established in the first reactor under step c) of theprocess of the invention, the feeds are switched back to the firstreactor and the conditions of the second reactor are changed to thesecond set of conditions.

The vapor product stream from the first reactor thus comprises themono-alkylene glycol and possibly heavier components, the latter may befor example di- and tri-ethylene glycol. However, because of thepreferential deposition of the heavier glycols onto the surface of thecatalyst in the first reactor, the amount of these ‘heavies’ in theproduct stream of step a) will be low. Greater amounts of heavierglycols may be present in the product mixture from step b). In bothcases the heavier glycols where present can optionally be removed via adistillation column (a ‘topping and tailing column’) where the puremono-ethylene glycol is withdrawn as a side-stream and these heavies aredrawn off as a separate stream and utilized, or incinerated as waste.

The nature of the two sets of conditions may vary, however generally theconditions will be such that a direct change from the first set ofconditions to the second set of conditions will cause the evaporation ofglycol deposited on the catalyst.

Most preferably the first reactor, and second reactor where present, isa microchannel apparatus such as described herein. This provides theadditional advantage of good control of the conditions to be changed.The first reactor may be in a first set of process microchannelsoperating under the first set of conditions, and then the conditions canbe changed by use of a heat transfer medium, flowing through heatexchange channels, to change, for example, the temperature conditions toprovide evaporation of the glycol. Two microchannel apparatus may beprovided working in tandem with the glycol-containing feed beingswitched between the two microchannel apparatus so that a continuousoperation can occur, with a first microchannel performing the vaporphase hydration while the second is in evaporation mode, and thenswitching the feed so that the second apparatus performs the reactionwhile the first performs the evaporation.

Reference is made to the publications U.S. Pat. No. 6,508,862 and WO2005/032693 which describe microchannel apparatus used in temperatureswing sorption for fluids. The apparatus and control mechanisms may bereadily adapted to operating the process of the present invention bythose skilled in the art.

This aspect of the process of the invention may additionally be utilizedin conjunction with the use of microchannel apparatus to performconversion of alkylene oxide to glycol as described above.

The present invention will now be illustrated by the following Examples.

EXAMPLES Example 1

This prophetic example describes how an embodiment of this invention maybe practiced.

In a 400,000 mt/a ethylene oxide plant the stream of recycle gas to thereactor system is 600 mt/h. This flow mainly consists of methane,ethylene, oxygen, argon, carbon dioxide and nitrogen. The temperature atthe reactor inlet is 140° C. and the pressure is 2000 kPa gauge.

In FIG. 3, over the catalyst inside the reactor 1, ethylene and oxygenare consumed in the production of ethylene oxide (EO) and carbon dioxide(CO₂). After scrubbing the reaction product gases with water to absorbEO in EO absorber 2, and scrubbing part of the recycle gas of CO₂ in CO₂absorber 3, feed ethylene, via line 4, and oxygen, via line 5, aresupplied to the recycle gas before entering the reactor 1. 37.5 mt/hethylene is fed to the recycle gas and 34.6 mt/h oxygen. From reactor 1through absorber 2 and absorber 3 and back to the reactor 1, all ofthese sections plus the interconnecting pipework form the recycle gasloop.

The oxygen is mixed with the recycle gas in mixer 7. Mixer 7 is amicrochannel device such as described herein with respect to FIG. 1 andFIG. 2. The microchannel devise ensures improved mixing of oxygen withrecycle gas through multiple small volumes of gas being mixed in theindividual microchannels reducing the impact of an explosion reaction.Explosions in such large volumes of flammable gases in a worldscale EOproduction facility have a huge impact and by use of the microchanneldevice in such a plant, the risk of an incident is decreased.

Example 2

This prophetic example describes how an embodiment of this invention maybe practiced.

In a 400,000 mt/a ethylene oxide plant the stream of recycle gas to thereactor system is 600 mt/h. This flow mainly consists of methane,ethylene, oxygen, argon, carbon dioxide and nitrogen. The temperature atthe reactor inlet is 140° C. and the pressure is 2000 kPa gauge. In FIG.4, over the catalyst inside the reactor 11, ethylene oxide and carbondioxide are produced. EO is scrubbed in the EO absorber 12 and part ofthe recycle gas is scrubbed of CO₂ in the CO₂ absorber 13. The absorbentused for EO scrubbing is typically water with a small concentration ofmonoethylene glycol (2-10 weight %). Water saturated with ethylene oxidevia line 15 from the bottom of the EO absorber 12 is fed to the top ofEO stripper 14. The bottoms flow, line 16, of EO stripper 14 isvirtually free of EO and recycled back to the top of EO absorber 13. Anethylene oxide-water mixture (typically containing 50 to almost 100weight % ethylene oxide) is boiled over the top of the EO stripper as avapor flow, shown by line 17, and is condensed into vessel 26.Optionally part of the condensed vapor can be refluxed to increase theEO concentration in the top of the EO stripper. Gases like methane, CO₂and ethylene are removed, via line 19, from the condensed water/ethyleneoxide mixture in a light ends column 18. For pure EO applications the EOis dehydrated and purified in EO purification column 20. Water or amixture of water and EO leaves the bottom of this column via line 25.The top vapor is condensed and largely refluxed and re-enters the columnvia line 22 from condensate collection/reflux vessel 21. Typically asmall EO flow is fed from the EO reflux vessel 21 to the glycol sectionas a bleed for light components (see line 23). The pure EO product flow(line 24) is taken from the top section of this column, in this examplea few trays below the reflux tray.

In this example the top of the EO stripper 14, the top strippercondensers, EO/water line 25, the light ends column 18, the top sectionof the EO purification column 20, and the EO reflux vessel 21 contain ahigh concentration of EO. To limit explosion hazard both EO condensersare microchannel apparatus such as described with respect to FIG. 1 andFIG. 2. They act as condensers according to the present invention. Inthe apparatus the total EO volume is divided into a large amount ofsmall volumes inside the microchannels. In addition to that, heattransfer is drastically increased, thus minimizing the risk of runawayreactions eventually leading to explosions. In this example themicrochannel condensers can optionally be integrated inside the EOstripper 14 and EO purification column 20 as a so-called cold fingerenabling internal reflux. Thus a large volume of EO in a reflux vesselis avoided and explosion risk is even further reduced.

Example 3

This prophetic example describes how an embodiment of this invention maybe practiced.

In a 400,000 mt/a ethylene oxide plant the stream of cycle gas to thereactor system is 600 mt/h. This flow mainly consists of methane,ethylene, oxygen, argon, carbon dioxide and nitrogen. The temperature atthe reactor inlet is 140° C. and the pressure is 2000 kPa gauge. In FIG.5, over the catalyst inside the reactor 31, ethylene oxide and carbondioxide are produced. EO is scrubbed in the EO absorber 32 and part ofthe recycle gas is scrubbed of CO₂ in the CO₂ absorber 33.

The absorbent used for CO₂ scrubbing is typically a cycling activatedhot carbonate solution. Absorbent saturated with CO₂ from the bottom ofthe absorber 33 is fed via line 35 to the top of CO₂ stripper 34. HereCO₂ is vented to atmosphere as a waste gas flow 37. On average this CO₂waste gasflow is 18 mt/h in this example. The bottoms flow 36 of the CO₂stripper 34 is lean in CO₂ and cycled back to the top of absorber 33.The vented CO₂ gasflow 37 can contain traces of hydrocarbons likeethylene and methane, in this example 0.1 weight % ethylene and 0.2weight % methane. Also traces of ethylene oxide can sometimes bedetected in this gas stream, although much lower in concentration thanpreviously mentioned hydrocarbons.

Nowadays more and more countries demand lower levels of hydrocarbonemissions and ethylene oxide emissions. Therefore the CO₂ waste gasstream is often given a post treatment to remove these components belowthe level mentioned in the environmental permit. Commonly usedtechnology in this field is oxidizing, in other words combustion, of thehydrocarbons in an oxidizer. This can be either a thermal or a catalyticoxidation process. In order to maintain a proper heat balance theseoxidizers are often operated in cycling mode. The system shown in theschematic diagram below is of such a reverse flow system. The gas flowssubsequently through two compartments A and B (filled line). Bothcompartments have a preheat zone and a combustion zone. The hydrocarbonsin the CO₂ flow are preheated and combusted in compartment A. Thepreheat zone in compartment A will thus cool down. The hot gas heats upthe preheat zone in compartment B to a temperature that allowscombustion. As soon as the desired temperature is reached in compartmentB, the direction of the gasflow is switched and flows through B and A inthe opposite direction (dotted line), and the reverse process takesplace.

The clean CO₂ gas flow 38 is vented to atmosphere or can be used forother applications. In such a cycling system the switching valves aresubject to mechanical stresses and are sensitive to mechanical or evenchemical (corrosion) failure. Since the plant has to comply with theenvironmental permits, the total EO unit has to be shut down in case offailure of the oxidizer, which has a huge economical impact.

In the present invention the two compartments A and B are replaced by asingle microchannel apparatus having a first set of processmicrochannels to receive the CO₂ waste gas stream and in which the gasstream is subjected to combustion temperatures in order to combust thevolatile hydrocarbon contaminants. The gas stream then flows into asecond set of process microchannels which are in thermal contact withthe first set and the hot outlet gas can directly heat up the cold gasfed to the combustion chamber. Thus switching is avoided and reliabilityand simplicity of the system is drastically increased.

Example 4

This prophetic example describes how an embodiment of this invention maybe practiced.

In a plant 400,000 mt/a ethylene oxide is produced in a combined EO andglycols plant. 200,000 mt/a of this ethylene oxide is fed to theintegrated glycol production unit. In FIG. 6 of such a glycol productionunit, ethylene oxide via line 41 is subsequently mixed with fresh water(fed via line 42) and recycle water (50) in vessel 43, preheated in heatexchangers 44, and is reacted without catalysis with water to formmono-ethylene glycol in reactor 45. Since EO not only reacts with waterto mono-ethylene glycol but simultaneously with glycols, not onlymono-ethylene glycol is formed but also the byproducts di-ethyleneglycol, tri-ethylene glycol and even higher glycols are formed. Theamount and ratio of these glycols is heavily determined by theconcentration of these glycols inside the reactor. High concentration ofwater favors a high yield of mono-ethylene glycol. On the other hand ata low concentration of water a lot of di-ethylene glycol, tri-ethyleneglycol and the heavier glycols are formed which is in most casesundesired. In this example, the water to EO ratio of the reactor feed isadjusted to be 10:1 to achieve a ratio of 10:1:0.1 mono-ethylene glycol:di-ethylene glycol:tri-ethylene glycol in the reactor outlet stream 58.

The water is not only used as feedstock to form glycols and as dilutionagent to control the ratio of glycols, but also acts as a heat sink tocontrol the outlet temperature of the reactor outlet stream, since thereactions in the glycol reactor are strongly exothermic. Since theproduct glycol is produced in an abundance of water the mixture needs tobe dehydrated before separation and purification of the glycol mixturecan be achieved. Dehydration is typically carried out in a train ofconcentrator and dehydrator columns 46. The water streams from the topof these columns are combined as recycle water (50) and recycled to thereactor feed. The water-free bottom stream 51 of dehydrator 46 is fed tothe glycol purification section formed by mono-ethylene glycol column47, di-ethylene glycol column 48 and tri-ethylene glycol column 49, andthe glycol mixture is separated into its four product steamsmono-ethylene glycol (52), di-ethylene glycol (54), tri-ethylene glycol(56) and heavier glycols (57), with intermediate bottoms streams 53 and55.

It is evident that the need for large quantities of water will lead to alot of equipment needed for dehydration, and the dehydration itself willdemand a lot of energy use in the form of steam used in the concentratorand dehydrator column reboilers. By making use of the present invention,the reaction of EO to mono-ethylene glycol is performed inside theprocess microchannels of a microchannel reactor. The temperature can beeasily controlled because of the excellent heat transfer, and a largeamount of water for heat sink is not needed anymore. The reaction to MEGcan be catalyzed to suppress the formation of di-ethylene glycol,tri-ethylene glycol and other heavy glycols. A catalyst may be presentin one or more process microchannels. Thus the number of dehydratorcolumns can be reduced and energy for dehydration can be saved. By usinga catalyst the selectivity to mono-ethylene glycol can additionally beincreased, enabling reduction of the size of glycol purificationequipment.

Example 5

A Co/Zn/Al hydrotalcite-type catalyst was prepared as follows: 24 g ofCo(NO₃)₂·6H₂O was dissolved in 200 ml demi-water, 93.8 g ofAl(NO₃)₃·9H₂O was dissolved in 300 ml demi-water and 124.2 g ofZn(NO₃)₂·6H₂O in 300 ml demiwater. These three solutions were mixedforming solution A and stored in a drip-flask. Then 70 g NaOH wasdissolved in 200 ml demi-water and 53 g Na₂CO₃ in 250 ml demiwater. Thelatter was heated to 50° C. until clear. Both Na solutions weresubsequently mixed in a 2 liter round bottom and stirred for 0.5 hourwhile cooling to <5° C. This is solution B. In the next step solution Awas added slowly (ca. 8 ml/min totaling 1.5 hours) to B while keepingthe temperature below 5° C. A thick pink gel was formed. After mixing ofA and B the resulting slurry was heated to 60° C. and stirred foranother 1.5 hours. Then the heater was turned off and stirring wascontinued for the night. The next day the slurry was filtered and washed3 times with demi-water. Half of the filter cake was dried at 120° C.,the other half was calcined at 425° C. for 12 hrs in air. The targetcomposition was CO₂Zn₁₀Al₆·(CO₃)_(x)·yH₂0.

Example 6

This prophetic example describes how an embodiment of this invention maybe practiced.

The microchannel reactor will be assembled in accordance with methodsknown from WO-A-2004/099113, and references cited therein.

A microchannel reactor will comprise process microchannels, heatexchange microchannels, and feed channels.

The process microchannel section will comprise a hydrolysis catalystcomprising cobalt, zinc and alumina as described above.

The process microchannel reactor will be filled with a hydrolysiscatalyst that will be prepared by milling and sieving ahydrotalcite-type catalyst. The catalyst will be firstly conditionedunder N₂ and H₂O_(g) for at least 1 hour at reaction temperature beforeadding the reaction gas mixture.

The process section will be heated at 275° C. by heat exchange with theheat exchange fluid flowing in the first heat exchange microchannel,while water is fed through an opening positioned at the upstream end ofthe process microchannels. This process section will be maintained at500 kPa.

Ethylene oxide gas will be fed through a second set of feed channelsupstream of the process microchannels. The molar ratio of ethylene oxideto water will be 1:10.

As an alternative, ethylene oxide and water (molar ratio 1 to 10) willbe fed into the microchannel process section using one feed channelupstream of the process section.

The product mixture exiting the process section, containing the desiredmono-ethylene glycol will be further processed and/or purified by aconventional method.

Example 7

This prophetic example describes how an embodiment of this invention maybe practiced.

The microchannel reactor will be assembled in accordance with methodsknown from WO-A-2004/099113, and references cited therein.

A microchannel reactor will comprise process microchannels, heatexchange microchannels, and feed channels.

The process microchannel section will comprise a hydrolysis catalystcomprising cobalt, zinc and alumina as described above.

The process microchannel reactor will be filled with a hydrolysiscatalyst that will be prepared by milling and sieving a hydrotalcitetype catalyst. The catalyst will be firstly conditioned under N₂ andH₂O_(g) for at least 1 hour at reaction temperature before adding thereaction gas mixture.

Two such microchannel reactors will be operated in swing mode inparallel, in which simultaneously one reactor is operated with EO/waterfeed to produce glycol and the other reactor is operated at highertemperature and lower pressure to evaporate condensed higher glycolsfrom the catalyst surface.

The process section will be heated at 275° C. by heat exchange with theheat exchange fluid flowing in the first heat exchange microchannel,while water is fed through an opening positioned at the upstream end ofthe process microchannels. This process section will be maintained at500 kPa.

Ethylene oxide gas will be fed through a second set of feed channelsupstream of the process microchannels. The molar ratio of ethylene oxideto water will be 1:10.

As an alternative ethylene oxide and water (molar ratio 1 to 10) will befed into the microchannel process section using one feed channelupstream of the process section.

Simultaneously the second microchannel reactor will be operated at 350°C. and 200 kPa without feeding ethylene oxide/water.

Conditions and feed of both parallel reactors will be changed every 30seconds.

The product mixture exiting the process section, containing the desiredmono-ethylene glycol may be further processed and/or purified by asuitable method.

Example 8

This prophetic example describes how an embodiment of this invention maybe practiced.

The microchannel reactor will be assembled in accordance with methodsknown from WO-A-2004/099113, and references cited therein.

A microchannel reactor will comprise process microchannels, heatexchange microchannels, and feed channels.

The process microchannel section will comprise a hydrolysis catalystcomprising cobalt, zinc and alumina as described above.

The process microchannel reactor will be filled with a hydrolysiscatalyst that will be prepared by milling and sieving a hydrotalcitetype catalyst. The catalyst will be firstly conditioned under N₂ andH₂O_(g) for at least 1 hour at reaction temperature before adding thereaction gas mixture.

The process section will be heated at 275° C. by heat exchange with theheat exchange fluid flowing in the first heat exchange microchannel,while water is fed through an opening positioned at the upstream end ofthe process microchannels. This process section will be maintained at500 kPa.

Ethylene oxide gas will be fed through a second set of feed channelsupstream of the process microchannels. The molar ratio of ethylene oxideto water will be 1:10.

As an alternative, ethylene oxide and water (molar ratio 1 to 10) willbe fed into the microchannel process section using one feed channelupstream of the process section.

The vapor phase product mixture exiting the process section, containingunreacted ethylene oxide, water, and the desired mono-ethylene glycolwill be further processed in a second set of parallel microchannelreactors operating in swing mode.

One reactor will be fed with the product mixture from the processsection and will operate at a lower temperature of 120° C. to enablecondensation of the monoethylene glycol, while the unreacted ethyleneoxide and water will be recycled back to the process microchannelreactor. The other parallel reactor will operate at an elevatedtemperature of 200° C. to vaporize condensed monoethylene glycol forfurther processing and purification. Conditions and feed of bothparallel reactors will be changed every 60 seconds.

The description titled “IMPROVEMENTS IN EPOXIDATION CATALYSTS ANDMETHODS”, which follows hereinafter, describes an invention andembodiments thereof which may suitably be applied in conjunction withthe invention and embodiments thereof described hereinbefore. Theinvention and embodiments thereof described hereinbefore may suitably beapplied in conjunction with the invention and embodiments thereofdescribed in the description hereinafter. It is to be understood thatthe invention and embodiments thereof described hereinbefore areindependent of, and may be practiced separately from the inventions andembodiments described hereinafter. It is also to be understood that theinvention and embodiments thereof described hereinafter are independentof, and may be practiced separately from the inventions and embodimentsdescribed hereinbefore. Further, it is to be understood that thedescription titled “IMPROVEMENTS IN EPOXIDATION CATALYSTS AND METHODS”is a self-contained description, which forms together with thedescription provided hereinbefore an integral disclosure of an inventionand embodiments thereof. FIGS. 1-6 referred to in the descriptionhereinafter are identical to FIGS. 1-6, respectively, referred tohereinbefore.

Improvements in Epoxidation Catalysts and Methods BACKGROUND OF THEINVENTION

Ethylene oxide and other olefin oxides are important industrialchemicals used as a feedstock for making such chemicals as ethyleneglycol, propylene glycol, ethylene glycol ethers, ethylene carbonate,ethanol amines and detergents. One method for manufacturing an olefinoxide is by olefin epoxidation, that is the catalyzed partial oxidationof the olefin with oxygen yielding the olefin oxide. The olefin oxide somanufactured may be reacted with water, an alcohol, carbon dioxide, oran amine to produce a 1,2-diol, a 1,2-diol ether, a 1,2-carbonate or analkanol amine. Such production of a 1,2-diol, a 1,2-diol ether, a1,2-carbonate or an alkanol amine is generally carried out separatelyfrom the manufacture of the olefin oxide, in any case the two processesare normally carried out in separate reactors.

In olefin epoxidation, a feed containing the olefin and oxygen is passedover a bed of catalyst contained within a reaction zone that ismaintained at certain reaction conditions. A commercial epoxidationreactor is generally in the form of a shell-and-tube heat exchanger, inwhich a plurality of substantially parallel elongated, relatively narrowtubes are filled with shaped catalyst particles to form a packed bed,and in which the shell contains a coolant. Irrespective of the type ofepoxidation catalyst used, in commercial operation the internal tubediameter is frequently in the range of from 20 to 40 mm, and the numberof tubes per reactor may range in the thousands, for example up to12,000.

Olefin epoxidation is generally carried out with a relatively low olefinconversion and oxygen conversion. Recycle of unconverted olefin andoxygen is normally applied in order to enhance the economics of theprocess. Generally the feed additionally comprises a large quantity ofso-called ballast gas to facilitate operation outside the explosionlimits. Ballast gas includes saturated hydrocarbons, in particularmethane and ethane. As a consequence, recycling generally involves thehandling of large quantities of process streams, which includes theunconverted olefin, unconverted oxygen and the ballast gas. Theprocessing of the recycle stream as normally applied in an olefinepoxidation plant is also fairly complex, as it involves olefin oxiderecovery, carbon dioxide removal, water removal and re-pressurizing. Theuse of ballast gas not only contributes to the cost of processing, italso reduces the epoxidation reaction rate.

The epoxidation catalyst generally contains the catalytically activespecies, typically a Group 11 metal (in particular silver) and promotercomponents, on a shaped carrier material. Shaped carrier materials aregenerally carefully selected to meet requirements of, for example,strength and resistance against abrasion, surface area and porosity. Theshaped carrier materials are generally manufactured by sinteringselected inorganic materials to the extent that they have the desiredproperties.

During the epoxidation, the catalyst is subject to a performancedecline, which represents itself by a loss in activity of the catalystand selectivity in the formation the desired olefin oxide. In responseto the loss of activity, the epoxidation reaction temperature may beincreased such that the production rate of the olefin oxide ismaintained. The operation of commercial reactors is normally limitedwith respect to the reaction temperature and when the applicabletemperature limit has been reached, the production of the olefin oxidehas to be interrupted for an exchange of the existing charge ofepoxidation catalyst for a fresh charge.

It would be of great value if improved epoxidation processes andimproved epoxidation reactors would become available.

SUMMARY OF THE INVENTION

The present invention provides such improved epoxidation processes andimproved epoxidation reactors. Embodiments of the present invention makeuse of a reactor which comprises a plurality of microchannels (“processmicrochannels” hereinafter). The process microchannels may be adaptedsuch that the epoxidation and optionally other processes can take placein the microchannels and that they are in a heat exchange relation withchannels adapted to contain a heat exchange fluid (“heat exchangechannels” hereinafter). A reactor comprising process microchannels isreferred to herein by using the term “microchannel reactor”. As usedherein, the term “Group 11” refers to Group 11 of the Periodic Table ofthe Elements.

In an embodiment, the present invention provides a method of installingan epoxidation catalyst in one or more process microchannels of amicrochannel reactor, which method comprises

depositing a Group 11 metal or a cationic Group 11 metal component on atleast a portion of the walls of the said process microchannels,

depositing one or more promoter components on at least a portion of thesame walls prior to, together with or subsequent to the deposition ofthe Group 11 metal or the cationic Group 11 metal component, and,

if a cationic Group 11 metal component is deposited, reducing at least aportion of the cationic Group 11 metal component.

In another embodiment, the invention provides a process for theepoxidation of an olefin comprising

installing an epoxidation catalyst in one or more process microchannelsof a microchannel reactor by

depositing a Group 11 metal or a cationic Group 11 metal component on atleast a portion of the walls of the said process microchannels;

depositing one or more promoter components on at least a portion of thesame walls prior to, together with or subsequent to the deposition ofthe Group 11 metal or the cationic Group 11 metal component; and,

if a cationic Group 11 metal component is deposited, reducing at least aportion of the cationic Group 11 metal component, and

reacting a feed comprising the olefin and oxygen in the presence of theepoxidation catalyst installed in the one or more process microchannels.

In another embodiment, the invention provides a process for thepreparation of a 1,2-diol, a 1,2-diol ether, a 1,2-carbonate or analkanol amine, which process comprises

installing an epoxidation catalyst in one or more process microchannelsof a microchannel reactor by

depositing a Group 11 metal or a cationic Group 11 metal component on atleast a portion of the walls of the said process microchannels;

depositing one or more promoter components on at least a portion of thesame walls prior to, together with or subsequent to the deposition ofthe Group 11 metal or the cationic Group 11 metal component; and,

if a cationic Group 11 metal component is deposited, reducing at least aportion of the cationic Group 11 metal component,

reacting a feed comprising the olefin and oxygen in the presence of theepoxidation catalyst installed in the one or more process microchannelsto produce an olefin oxide, and

converting the olefin oxide with water, an alcohol, carbon dioxide or anamine to form the 1,2-diol, 1,2-diol ether, 1,2-carbonate or alkanolamine.

In another embodiment, the invention provides a method of installing anepoxidation catalyst in one or more process microchannels of amicrochannel reactor, which method comprises

introducing into the one or more process microchannels a dispersion ofthe catalyst in an essentially non-aqueous diluent, and

removing at least a portion of the diluent.

In another embodiment, the invention provides a process for theepoxidation of an olefin comprising

installing an epoxidation catalyst in one or more process microchannelsof a microchannel reactor by

introducing into the one or more process microchannels a dispersion ofthe catalyst in an essentially non-aqueous diluent; and

removing at least a portion of the diluent, and

reacting a feed comprising the olefin and oxygen in the presence of theepoxidation catalyst installed in the one or more process microchannels.

In another embodiment, the invention provides a process for thepreparation of a 1,2-diol, a 1,2-diol ether, 1,2-carbonate or an alkanolamine, which process comprises

installing an epoxidation catalyst in one or more process microchannelsof a microchannel reactor by

introducing into the one or more process microchannels a dispersion ofthe catalyst in an essentially non-aqueous diluent; and

removing at least a portion of the diluent,

reacting a feed comprising the olefin and oxygen in the presence of theepoxidation catalyst installed in the one or more process microchannelsto produce an olefin oxide, and

converting the olefin oxide with water, an alcohol, carbon dioxide or anamine to form the 1,2-diol, 1,2-diol ether, 1,2-carbonate or alkanolamine.

In another embodiment, the invention provides a method of preparing aparticulate epoxidation catalyst, which method comprises depositing aGroup 11 metal and one or more promoter components on a particulatecarrier material having a pore size distribution such that pores withdiameters in the range of from 0.2 to 10 μm represent at least 70% ofthe total pore volume.

In another embodiment, the invention provides a particulate epoxidationcatalyst, which catalyst comprises a Group 11 metal and one or morepromoter components deposited on a particulate carrier material having apore size distribution such that pores with diameters in the range offrom 0.2 to 10 μm represent at least 70% of the total pore volume.

In another embodiment, the invention provides a process for theepoxidation of an olefin comprising reacting a feed comprising theolefin and oxygen in the presence an epoxidation catalyst installed inone or more process microchannels of a microchannel reactor, whichepoxidation catalyst comprises a Group 11 metal and one or more promotercomponents deposited on a particulate carrier material having a poresize distribution such that pores with diameters in the range of from0.2 to 10 μm represent at least 70% of the total pore volume.

In another embodiment, the invention provides a process for thepreparation of a 1,2-diol, a 1,2-diol ether, a 1,2-carbonate or analkanol amine, which process comprises

reacting a feed comprising the olefin and oxygen in the presence anepoxidation catalyst installed in one or more process microchannels of amicrochannel reactor to produce an olefin oxide, which epoxidationcatalyst comprises a Group 11 metal and one or more promoter componentsdeposited on a particulate carrier material having a pore sizedistribution such that pores with diameters in the range of from 0.2 to10 μm represent at least 70% of the total pore volume, and

converting the olefin oxide with water, an alcohol, carbon dioxide or anamine to form the 1,2-diol, 1,2-diol ether, 1,2-carbonate or alkanolamine.

In another embodiment, the invention provides a process for theepoxidation of an olefin comprising reacting a feed comprising theolefin and oxygen in a total quantity of at least 50 mole-%, relative tothe total feed, in the presence an epoxidation catalyst contained in oneor more process microchannels of a microchannel reactor.

In another embodiment, the invention provides a process for thepreparation of a 1,2-diol, a 1,2-diol ether, a 1,2-carbonate or analkanol amine, which process comprises

reacting a feed comprising the olefin and oxygen in a total quantity ofat least 50 mole-%, relative to the total feed, in the presence anepoxidation catalyst contained in one or more process microchannels of amicrochannel reactor to produce an olefin oxide, and

converting the olefin oxide with water, an alcohol, carbon dioxide or anamine to form the 1,2-diol, 1,2-diol ether, 1,2-carbonate or alkanolamine.

In another embodiment, the invention provides a process for theepoxidation of an olefin comprising reacting a feed comprising theolefin and oxygen in the presence an epoxidation catalyst contained inone or more process microchannels of a microchannel reactor, andapplying conditions for reacting the feed such that the conversion ofthe olefin or the conversion of oxygen is at least 90 mole-%.

In another embodiment, the invention provides a process for thepreparation of a 1,2-diol, a 1,2-diol ether, a 1,2-carbonate or analkanol amine, which process comprises

reacting a feed comprising the olefin and oxygen in the presence anepoxidation catalyst contained in one or more process microchannels of amicrochannel reactor to produce an olefin oxide, and applying conditionsfor reacting the feed such that the conversion of the olefin or theconversion of oxygen is at least 90 mole-%, and

converting the olefin oxide with water, an alcohol, carbon dioxide or anamine to form the 1,2-diol, 1,2-diol ether, 1,2-carbonate or alkanolamine.

In another embodiment, the invention provides a method of rejuvenatingan epoxidation catalyst, which method comprises

washing the catalyst with an aqueous liquid, and

depositing one or more promoter components on the washed catalyst.

In another embodiment, the invention provides a process for theepoxidation of an olefin comprising

rejuvenating an epoxidation catalyst which has been used in anepoxidation process, which rejuvenation comprises

washing the catalyst with an aqueous liquid; and

depositing one or more promoter components on the washed catalyst, and

reacting a feed comprising the olefin and oxygen in the presence of therejuvenated catalyst.

In another embodiment, the invention provides a process for thepreparation of a 1,2-diol, a 1,2-diol ether, a 1,2-carbonate or analkanol amine, which process comprises

rejuvenating an epoxidation catalyst which has been used in anepoxidation process, which rejuvenation comprises

washing the catalyst with an aqueous liquid; and

depositing one or more promoter components on the washed catalyst,

reacting a feed comprising the olefin and oxygen in the presence of therejuvenated catalyst to produce an olefin oxide, and

converting the olefin oxide with water, an alcohol, carbon dioxide or anamine to form the 1,2-diol, 1,2-diol ether, 1,2-carbonate or alkanolamine.

In another embodiment, the invention provides a reactor suitable for theepoxidation of an olefin, which reactor is a microchannel reactorcomprising one or more process microchannels comprising

an upstream end,

a downstream end,

a first section which is adapted to contain an epoxidation catalyst, toreceive a feed comprising an olefin and oxygen, and to cause conversionof at least a portion of the feed to form an olefin oxide in thepresence of the epoxidation catalyst, and

a second section positioned downstream of the first section which isadapted to receive and to cause quenching of the olefin oxide by heatexchange with a heat exchange fluid.

The reactor of the latter embodiment may comprise additionally one ormore first heat exchange channels adapted to exchange heat with thefirst section of the said process microchannels, and one or more secondheat exchange channels adapted to exchange heat with the second sectionof the said process microchannels.

In another embodiment, the invention provides a process for theepoxidation of an olefin comprising

reacting a feed comprising an olefin and oxygen in the presence of anepoxidation catalyst contained in a first section of one or more processmicrochannels of a microchannel reactor to thereby form an olefin oxide,and

quenching the olefin oxide in a second section of the one or moreprocess microchannels positioned downstream of the first section by heatexchange with a heat exchange fluid.

In another embodiment, the invention provides a process for thepreparation of a 1,2-diol, a 1,2-diol ether, a 1,2-carbonate or analkanol amine, which process comprises

reacting a feed comprising an olefin and oxygen in the presence of anepoxidation catalyst contained in a first section of one or more processmicrochannels of a microchannel reactor to thereby form an olefin oxide,

quenching the olefin oxide in a second section of the one or moreprocess microchannels positioned downstream of the first section by heatexchange with a heat exchange fluid, and

converting the olefin oxide with water, an alcohol, carbon dioxide or anamine to form the 1,2-diol, 1,2-diol ether, 1,2-carbonate or alkanolamine.

In another embodiment, the invention provides a process for theepoxidation of an olefin comprising

reacting a feed comprising an olefin and oxygen in the presence of anepoxidation catalyst to thereby form a first mixture comprising theolefin oxide and carbon dioxide,

quenching the first mixture, typically, by heat exchange with a heatexchange fluid, and

converting the quenched first mixture to form a second mixturecomprising the olefin oxide and a 1,2-carbonate.

Preferably, in this embodiment, the invention provides a process for theepoxidation of an olefin comprising

reacting a feed comprising an olefin and oxygen in the presence of anepoxidation catalyst contained in a first section of one or more processmicrochannels of a microchannel reactor to thereby form a first mixturecomprising the olefin oxide and carbon dioxide,

quenching the first mixture in a first intermediate section of the oneor more process microchannels positioned downstream of the first sectionby heat exchange with a heat exchange fluid, and

converting in a second section of the one or more process microchannelspositioned downstream of the first intermediate section the quenchedfirst mixture to form a second mixture comprising the olefin oxide and a1,2-carbonate.

In this embodiment, when the second mixture is formed at least partly asa gaseous phase, the process may additionally comprise condensing in athird section of the one or more process microchannels positioneddownstream of the second section at least a portion of the secondmixture comprising the olefin oxide and the 1,2-carbonate. Preferably,in cases that the second mixture comprises water at least partly as agaseous phase, the process may additionally comprise condensing,typically in the third section, at least a portion of such water presentin the second mixture.

In another embodiment, the invention provides a process for thepreparation of a 1,2-diol, a 1,2-diol ether, a 1,2-carbonate or analkanol amine, which process comprises

reacting a feed comprising an olefin and oxygen in the presence of anepoxidation catalyst to thereby form a first mixture comprising theolefin oxide and carbon dioxide,

quenching the first mixture, typically, by heat exchange with a heatexchange fluid,

converting the quenched first mixture to form a second mixturecomprising the olefin oxide and a 1,2-carbonate, and

converting the second mixture with water, an alcohol, carbon dioxide oran amine to form the 1,2-diol, 1,2-diol ether, 1,2-carbonate or alkanolamine.

In this embodiment, the second mixture is preferably converted withwater to form the 1,2-diol.

In another embodiment, the invention provides a reactor suitable for thepreparation of a 1,2-diol, a 1,2-diol ether, a 1,2-carbonate or analkanol amine, which reactor is a microchannel reactor comprising one ormore process microchannels comprising

an upstream end,

a downstream end,

a first section which is adapted to contain an epoxidation catalyst, toreceive a feed comprising an olefin and oxygen, and to cause conversionof at least a portion of the feed to form an olefin oxide in thepresence of the epoxidation catalyst, and

a second section positioned downstream of the first section which isadapted to receive the olefin oxide; to receive water, an alcohol,carbon dioxide or an amine; and to cause conversion of the olefin oxideto form the 1,2-diol, 1,2-diol ether, 1,2-carbonate or alkanol amine.

The reactor of the latter embodiment may comprise additionally one ormore first heat exchange channels adapted to exchange heat with thefirst section of the said process microchannels, and

one or more second heat exchange channels adapted to exchange heat withthe second section of the said process microchannels.

Further, the one or more process microchannels may comprise additionallyan intermediate section downstream from the first section and upstreamfrom the second section, which intermediate section is adapted tocontrol the temperature of the olefin oxide. In particular, the reactormay comprise additionally one or more third heat exchange channelsadapted to exchange heat with the intermediate section of the saidprocess microchannels.

The second section may additionally be adapted to contain a catalyst.

In another embodiment, the invention provides a process for thepreparation of a 1,2-diol, a 1,2-diol ether, a 1,2-carbonate or analkanol amine, which process comprises

reacting a feed comprising an olefin and oxygen in the presence of anepoxidation catalyst contained in a first section of one or more processmicrochannels of a microchannel reactor to form an olefin oxide, and

converting the olefin oxide with water, an alcohol, carbon dioxide or anamine to form the 1,2-diol, 1,2-diol ether, 1,2-carbonate or alkanolamine in a second section of the one or more process microchannelspositioned downstream of the first section.

In another embodiment, the invention provides a reactor suitable for thepreparation of a 1,2-diol, which reactor is a microchannel reactorcomprising one or more process microchannels comprising

an upstream end,

a downstream end,

a first section which is adapted to contain an epoxidation catalyst, toreceive a feed comprising an olefin and oxygen, and to cause conversionof at least a portion of the feed to form an olefin oxide in thepresence of the epoxidation catalyst,

a second section positioned downstream of the first section which isadapted to receive the olefin oxide, to receive carbon dioxide, and tocause conversion of the olefin oxide to form a 1,2-carbonate, and

a third section positioned downstream of the first section which isadapted to receive the 1,2-carbonate, to receive water or an alcohol,and to cause conversion of the 1,2-carbonate to form a 1,2-diol.

The reactor of the latter embodiment may comprise additionally one ormore first heat exchange channels adapted to exchange heat with thefirst section of the said process microchannels,

one or more second heat exchange channels adapted to exchange heat withthe second section of the said process microchannels, and one or morethird heat exchange channels adapted to exchange heat with the thirdsection of the said process microchannels.

Further, the one or more process microchannels may comprise additionallya first intermediate section downstream from the first section andupstream from the second section, which first intermediate section isadapted to control the temperature of the olefin oxide, and

a second intermediate section downstream from the second section andupstream from the third section, which second intermediate section isadapted to control the temperature of the 1,2-carbonate.

In particular, the reactor may comprise additionally one or more fourthheat exchange channels adapted to exchange heat with the firstintermediate section of the said process microchannels, and one or morefifth heat exchange channels adapted to exchange heat with the secondintermediate section of the said process microchannels.

The second section may additionally be adapted to contain acarboxylation catalyst.

In another embodiment, the invention provides a process for thepreparation of a 1,2-diol, which process comprises

reacting a feed comprising an olefin and oxygen in the presence anepoxidation catalyst contained in a first section of one or more processmicrochannels of a microchannel reactor to form an olefin oxide,

converting the olefin oxide with carbon dioxide to form a 1,2-carbonatein a second section of the one or more process microchannels positioneddownstream of the first section, and

converting the 1,2-carbonate with water or an alcohol to form the1,2-diol in a third section of the one or more process microchannelspositioned downstream of the second section.

In another embodiment, the invention provides a process for thepreparation of a 1,2-diol, a 1,2-diol ether, a 1,2-carbonate or analkanol amine, which process comprises reacting in one or more processmicrochannels of a microchannel reactor an olefin oxide with water, analcohol, carbon dioxide or an amine to form the 1,2-diol, 1,2-diolether, 1,2-carbonate or alkanol amine.

In another embodiment, the invention provides a process for thepreparation of a 1,2-diol, which process comprises converting in one ormore process microchannels of a microchannel reactor a 1,2-carbonatewith water or an alcohol to form the 1,2-diol.

DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic of a microchannel reactor and its mainconstituents.

FIG. 2 shows a schematic of a typical example of a repeating unit whichcomprises process microchannels and heat exchange channels and itsoperation when in use in the practice of the invention. A microchannelreactor of this invention may comprise a plurality of such repeatingunits.

FIG. 3 shows a schematic drawing of an example of a process for thepreparation of ethylene oxide.

FIG. 4 shows a schematic drawing of an example of a process for thepurification of ethylene oxide.

FIG. 5 shows a schematic drawing of an example of a typical process forthe removal of combustible volatile contaminant materials from a processstream.

FIG. 6 shows a schematic drawing of an example of a glycol productionunit.

DETAILED DESCRIPTION OF THE INVENTION

The use of a microchannel reactor in accordance with this inventionleads to one or more of the following advantages:

the epoxidation catalyst does not necessarily involve the use a shapedcarrier, which can eliminate the need for a step for producing a shapedcarrier.

quenching of the olefin oxide inside the process microchannel enablesoperation under conditions which may be within explosion limits whensuch conditions would be applied in a conventional shell-and-tube heatexchanger reactor. Such conditions may be achieved by contacting anoxygen rich feed component with an olefin rich feed component within theprocess microchannels, which oxygen rich feed component and olefin richfeed component are normally outside the explosion limits. Quenchinginside the process microchannels also decreases the formation ofbyproducts, such as aldehydes and carboxylic acids.

the epoxidation within the process microchannels can advantageously becarried out at conditions of high total concentration of the olefin,oxygen and the olefin oxide, which can lead to a higher epoxidation rateand/or lower epoxidation reaction temperature. Lowering the epoxidationreaction temperature can lead to improved selectivity and improvedcatalyst life. Employing conditions of high total concentration of theolefin, oxygen and the olefin oxide can also eliminate the need of usinga ballast gas, which provides more efficient processing and reduction ofthe costs of recycling.

the epoxidation carried out in process microchannels may be operated ata high conversion level of oxygen or the olefin oxide. In particularwhen the process is carried out at a high olefin conversion level, it isadvantageous to operate the epoxidation process in once-throughoperation, which implies that no recycle stream is applied. In addition,it is advantageous that in such case air may be fed to the processmicrochannels, instead of oxygen separated from air, which can eliminatethe need for an air separation unit.

a rejuvenation technique can be carried out while the epoxidationcatalyst is maintained inside the reactor, eliminating the need for theexchange of catalysts.

carrying out the olefin epoxidation inside the process microchannelsenables quenching inside the same process microchannels and conversionof the co-formed carbon dioxide with at least a portion of the producedolefin oxide, and optionally condensing a liquid, typically aqueous,mixture comprising unconverted olefin oxide and the 1,2-carbonate. Inrespect of its composition, a remaining gaseous stream which maycomprise unconverted ethylene and oxygen is suitable for recycle. Thiscan reduce the complexity of the further processing of product andrecycle streams, eliminating the need for, for example, an olefin oxiderecovering unit and a carbon dioxide removal unit.

carrying out the olefin epoxidation inside the process microchannelsenables conversion of the formed olefin oxide inside the same processmicrochannels to 1,2-diol, 1,2-diol ether, 1,2-carbonate or alkanolamine. This can eliminate the need for additional reactors for suchfurther conversion. It can also eliminate the need for an olefin oxiderecovering unit and/or a carbon dioxide removal unit, and it can reducethe need for heat exchanging equipment. Hence, it can reduce thecomplexity of the additional processing conventionally applied in amanufacturing plant, for example for product recovery. Conversion of theolefin oxide inside the process microchannels also decreases theformation of byproducts, such as aldehydes and carboxylic acids.

carrying out the conversion of an olefin oxide into a 1,2-diol, a1,2-diol ether, a 1,2-carbonate or an alkanol amine inside the processmicrochannels of a microchannel reactor has the advantageous effect thatthere is no need to have the reactants present in the reactor in arelatively high dilution. When such reactions are carried out inconventional equipment, a relatively high degree of dilution isfrequently applied, for example by having a relatively large excess of,for example, water, alcohol or amine present as diluent. The relativelylarge amount of diluent, added to the reaction mixture as a relativelycold component, acts as a heat sink. Acting as a heat sink meanspreventing a large increase of the temperature by having the capabilityto absorb the heat of reaction. The use of a relatively large amount ofdiluent is a disadvantage, in that it increases the reaction timesand/or reactor volumes and it creates relatively large recycle streams,which all influence the process economics in a unfavorable manner. Bythe application of a microchannel reactor, a high degree of dilution maybe avoided. However, in the presence of less diluent, in particular lessexcess of water, alcohol or amine, the selectivity to the desiredproduct will become less.

Microchannel reactors suitable for use in this invention and theiroperation have been described in WO-A-2004/099113, WO-A-01/12312,WO-01/54812, U.S. Pat. No. 6,440,895, U.S. Pat. No. 6,284,217, U.S. Pat.No. 6,451,864, U.S. Pat. No. 6,491,880, U.S. Pat. No. 6,666,909, U.S.Pat. No. 6,811,829, U.S. Pat. No. 6,851,171, U.S. Pat. No. 6,494,614,U.S. Pat. No. 6,228,434 and U.S. Pat. No. 6,192,596, which areincorporated herein by reference. Methods by which the microchannelreactor may be manufactured, loaded with catalyst and operated, asdescribed in these references, may generally be applicable in thepractice of the present invention.

With reference to FIG. 1, microchannel reactor 100 may be comprised of aprocess header 102, a plurality of process microchannels 104, and aprocess footer 108. The process header 102 provides a passageway forfluid to flow into the process microchannels 104. The process footer 108provides a passageway for fluid to flow from the process microchannels104.

The number of process microchannels contained in a microchannel reactormay be very large. For example, the number may be up to 10⁵, or even upto 10⁶ or up to 2×10⁶. Normally, the number of process microchannels maybe at least 10 or at least 100, or even at least 1000.

The process microchannels are typically arranged in parallel, forexample they may form an array of planar microchannels. The processmicrochannels may have at least one internal dimension of height orwidth of up to 15 mm, for example from 0.05 to 10 mm, in particular from0.1 to 5 mm, more in particular from 0.5 to 2 mm. The other internaldimension of height or width may be, for example, from 0.1 to 100 cm, inparticular from 0.2 to 75 cm, more in particular from 0.3 to 50 cm. Thelength of the process microchannels may be, for example, from 1 to 500cm, in particular from 2 to 300 cm, more in particular from 3 to 200 cm,or from 5 to 100 cm.

The microchannel reactor 100 additionally comprises heat exchangechannels (not shown in FIG. 1) which are in heat exchange contact withthe process microchannels 104. The heat exchange channels may also bemicrochannels. The microchannel reactor is adapted such that heatexchange fluid can flow from heat exchange header 110 through the heatexchange channels to heat exchange footer 112. The heat exchangechannels may be aligned to provide a flow in a co-current,counter-current or, preferably, cross-current direction, relative to aflow in the process microchannels 104. The cross-current direction is asindicated by arrows 114 and 116.

The heat exchange channels may have at least one internal dimension ofheight or width of up to 15 mm, for example from 0.05 to 10 mm, inparticular from 0.1 to 5 mm, more in particular from 0.5 to 2 mm. Theother internal dimension of height or width may be, for example, from0.1 to 100 cm, in particular from 0.2 to 75 cm, more in particular from0.3 to 50 cm. The length of the heat exchange channels may be, forexample, from 1 to 500 cm, in particular from 2 to 300 cm, more inparticular from 3 to 200 cm, or from 5 to 100 cm.

The separation between a process microchannel 104 and the next adjacentheat exchange channel may be in the range of from 0.05 mm to 5 mm, inparticular from 0.2 to 2 mm.

In some embodiments of this invention, there is provided for first heatexchange channels and second heat exchange channels, or first heatexchange channels, second heat exchange channels and third heat exchangechannels, or even up to fifth heat exchange channels, or even furtherheat exchange channels. Thus, in such cases, there is a plurality ofsets of heat exchange channels, and accordingly there may be a pluralityof heat exchange headers 110 and heat exchange footers 112, whereby thesets of heat exchange channels may be adapted to receive heat exchangefluid from a heat exchange header 110 and to deliver heat exchange fluidinto a heat exchange footer 112.

The process header 102, process footer 108, heat exchange header 110,heat exchange footer 112, process microchannels 104 and heat exchangechannels may independently be made of any construction material whichprovides sufficient strength, dimensional stability and heat transfercharacteristics to permit operation of the processes in accordance withthis invention. Suitable construction materials include, for example,steel (for example stainless steel and carbon steel), monel, titanium,copper, glass and polymer compositions. The kind of heat exchange fluidis not material to the present invention and the heat exchange fluid maybe selected from a large variety. Suitable heat exchange fluids includesteam, water, air and oils. In embodiments of the invention whichinclude a plurality of sets of heat exchange channels, such sets of heatexchange channels may operate with different heat exchange fluids orwith heat exchange fluids having different temperatures.

A microchannel reactor according to the invention may comprise aplurality of repeating units comprising one or more processmicrochannels and one or more heat exchange channels. Reference is nowmade to FIG. 2, which shows a typical repeating unit and its operation.

Process microchannels 210 have an upstream end 220 and a downstream end230 and may comprise of a first section 240 which may contain a catalyst(not drawn), for example an epoxidation catalyst. First section 240 maybe in heat exchange contact with first heat exchange channel 250,allowing heat exchange between first section 240 of process microchannel210 and first heat exchange channel 250. The repeating unit may comprisefirst feed channel 260 which ends into first section 240 through one ormore first orifices 280. Typically one or more first orifices 280 may bepositioned downstream relative to another first orifice 280. Duringoperation, feed comprising the olefin and oxygen may enter into firstsection 240 of process microchannel 210 through an opening in upstreamend 220 and/or through first feed channel 260 and one or more firstorifices 280.

Process microchannels 210 may comprise a second section 340 which may ormay not be adapted to contain a catalyst. Second section 340 may or maynot contain a catalyst, as described herein. Second section 340 ispositioned downstream of first section 240. Second section 340 may be inheat exchange contact with second heat exchange channel 350, allowingheat exchange between second section 340 of process microchannel 210 andsecond heat exchange channel 350. In some embodiments second section 340is adapted to quench olefin oxide obtained in and received from firstsection 240 by heat exchange with a heat exchange fluid in second heatexchange channel 350. Quenching may be achieved in one or more stages bythe presence of a plurality of second heat exchange channels 350, forexample two or three or four. Such a plurality of second heat exchangechannels 350 may be adapted to contain heat exchange fluids havingdifferent temperatures, in particular such that in downstream directionof second section 340 heat exchange takes place with a second heatexchange channel 350 containing a heat exchange fluid having a lowertemperature. The repeating unit may comprise second feed channel 360which ends into second section 340 through one or more second orifices380. During operation, feed may enter into second section 340 fromupstream in process microchannel 210 and through second feed channel 360and one or more second orifices 380. Typically one or more secondorifices 380 may be positioned downstream relative to another secondorifice 380. In embodiments in which second section 340 is adapted foraccommodating conversion of olefin oxide to 1,2-diol, 1,2-diol ether,1,2-carbonate or alkanol amine, feed entering during operation throughsecond feed channel 360 and one or more second orifices 380 may comprisewater, the alcohol, carbon dioxide or the amine. Also, catalyst may befed through second feed channel 360 and one or more second orifices 380.If desirable, a separate set of second feed channel (not drawn) with oneor more second orifices (not drawn) may be present in order toaccommodate separate feeding of feed and catalyst.

The first and second feed channels 260 or 360 in combination with firstand second orifices 280 or 380, whereby one or more first or secondorifices 280 or 380 are positioned downstream to another first or secondorifice 280 or 380, respectively, allow for replenishment of a reactant.Replenishment of a reactant is a feature in some embodiments of thisinvention.

Process microchannels 210 may comprise an intermediate section 440,which is positioned downstream of first section 240 and upstream ofsecond section 340. Intermediate section 440 may be in heat exchangecontact with third heat exchange channel 450, allowing heat exchangebetween intermediate section 440 of process microchannel 210 and thirdheat exchange channel 450. In some embodiments intermediate section 440is adapted to quench olefin oxide obtained in and received from firstsection 240 by heat exchange with a heat exchange fluid in third heatexchange channel 450. Quenching may be achieved in stages by thepresence of a plurality of third heat exchange channels 450, for exampletwo or three or four. Such a plurality of third heat exchange channels450 may be adapted to contain heat exchange fluids having differenttemperatures, in particular such that in downstream direction ofintermediate section 440 heat exchange takes place with a third heatexchange channel 450 containing a heat exchange fluid having a lowertemperature.

In some embodiments, process microchannel 210 may comprise a thirdsection (not drawn) downstream of second section 340, and optionally asecond intermediate section (not drawn) downstream of second section 340and upstream of the third section. The third section may or may not beadapted to contain a catalyst. The third section may or may not containa catalyst, as described herein. The third section may be in heatexchange contact with a fourth heat exchange channel (not drawn),allowing heat exchange between the third section of the processmicrochannel 210 and fourth heat exchange channel. The secondintermediate section may be in heat exchange contact with a fifth heatexchange channel (not drawn), allowing heat exchange between the secondintermediate section of the process microchannel 210 and fifth heatexchange channel. The repeating unit may comprise a third feed channel(not drawn) which ends into the third section through one or more thirdorifices (not drawn). Typically one or more third orifices may bepositioned downstream relative to another third orifice. Duringoperation, feed may enter into the third section from upstream inprocess microchannel 210 and through the third feed channel and the oneor more third orifices. In embodiments in which the third section isadapted for accommodating conversion of 1,2-carbonate into 1,2-diol,feed entering during operation through the third feed channel and theone or more third orifices may comprise water, an alcohol, or analcohol/water mixture. Also, catalyst may be fed through the third feedchannel and the one or more third orifices. If desirable, a separate setof third feed channels (not drawn) with one or more third orifices (notdrawn) may be present in order to accommodate separate feeding of feedand catalyst.

The feed channels may be microchannels. They may have at least oneinternal dimension of height or width of up to 15 mm, for example from0.05 to 10 mm, in particular from 0.1 to 5 mm, more in particular from0.5 to 2 mm. The other internal dimension of height or width may be, forexample, from 0.1 to 100 cm, in particular from 0.2 to 75 cm, more inparticular from 0.3 to 50 cm. The length of the feed channels may be,for example, from 1 to 250 cm, in particular from 2 to 150 cm, and moreparticularly from 3 to 100 cm, or from 5 to 50 cm.

The length of the sections of the process microchannels may be selectedindependently of each other, in accordance with, for example, the heatexchange capacity needed or the quantity of catalyst which may becontained in the section. The lengths of the sections are preferably atleast 1 cm, or at least 2 cm, or at least 5 cm. The lengths of thesections are preferably at most 250 cm, or at most 150 cm, or at most100 cm, or at most 50 cm. Other dimensions of the sections are dictatedby the corresponding dimensions of process microchannel 210.

The microchannel reactor of this invention may be manufactured usingknown techniques, for example conventional machining, laser cutting,molding, stamping and etching and combinations thereof. The microchannelreactor of this invention may be manufactured by forming sheets withfeatures removed which allow passages. A stack of such sheets may beassembled to form an integrated device, by using known techniques, forexample diffusion bonding, laser welding, cold welding, diffusionbrazing, and combinations thereof. The microchannel reactor of thisinvention comprises appropriate headers, footers, valves, conduit lines,and other features to control input of reactants, output of product, andflow of heat exchange fluids. These are not shown in the drawings, butthey can be readily provided by those skilled in the art. Also, theremay be further heat exchange equipment (not shown in the drawings) fortemperature control of feed, in particular for heating feed or feedcomponents, before it enters the process microchannels, or fortemperature control of product, in particular for quenching product,after it has left the process microchannels. Such further heat exchangeequipment may be integral with the microchannel reactor, but moretypically it will be separate equipment. These are not shown in thedrawings, but they can be readily provided by those skilled in the art.Heat integration may be applied, for example by using reaction heat ofthe epoxidation process for heating feed components, or for otherheating purposes.

Typically, the epoxidation catalysts are solid catalysts under theconditions of the epoxidation reaction. Such epoxidation catalyst, andany other solid catalysts as appropriate, may be installed by any knowntechnique in the designated section of the process microchannels. Thecatalysts may form a packed bed in the designated section of the processmicrochannel and/or they may form a coating on at least a portion of thewall of the designated section of the process microchannels. The skilledperson will understand that the coating will be positioned on theinterior wall of the process microchannels. Alternatively oradditionally, one or more of the catalysts may be in the form of acoating on inserts which may be placed in the designated section of theprocess microchannels. Coatings may be prepared by any depositionmethod, such as wash coating or vapor deposition. In some embodiments,the epoxidation catalyst may not be a solid catalyst under theconditions of the epoxidation, in which case the epoxidation catalystmay be fed to the designated section of the process microchannelstogether with one or more components of the epoxidation feed and maypass through the process microchannels along with the epoxidationreaction mixture.

The epoxidation catalyst which may be used in this invention istypically a catalyst which comprises one or more Group 11 metals. TheGroup 11 metals may be selected from the group consisting of silver andgold. Preferably, the Group 11 metal comprises silver. In particular,the Group 11 metal comprises silver in a quantity of at least 90% w,more in particular at least 95% w, for example at least 99% w, or atleast 99.5% w, calculated as the weight of silver metal relative to thetotal weight of the Group 11 metal, as metal. Typically, the epoxidationcatalyst additionally comprises one or more promoter components. Moretypically, the epoxidation catalyst comprises the Group 11 metal, one ormore promoter components and additionally one or more componentscomprising one or more further elements. In some embodiments, theepoxidation catalyst may comprise a carrier material on which the Group11 metal, any promoter components and any components comprising one ormore further elements may be deposited. Suitable promoter components andsuitable components comprising one or more further elements and suitablecarrier materials may be as described hereinafter.

In an embodiment, the present invention provides a method of installingan epoxidation catalyst in one or more process microchannels of amicrochannel reactor, which method comprises depositing one or moreGroup 11 metals or one or more cationic Group 11 metal components on atleast a portion of the walls of the said process microchannels,depositing one or more promoter components on at least the same wallsprior to, together with or subsequent to the deposition of the Group 11metal(s) or the cationic Group 11 metal component(s), and, if a cationicGroup 11 metal component is deposited, reducing at least a portion ofthe cationic Group 11 metal component(s).

Group 11 metal may be deposited on at least a portion of the walls ofthe process microchannels by contacting the walls with a liquidcontaining dispersed Group 11 metal, for example a Group 11 metal sol,and removing the liquid, for example by evaporation, while leaving Group11 metal on the wall. Such deposition may be carried out more than once,for example two times or three times, to accomplish the deposition of adesired amount of Group 11 metal. The quantity of Group 11 metal in suchliquid may be in the range of from 1 to 30% w, in particular from 2 to15% w, relative to the weight of the liquid. The liquid may compriseadditives, such as dispersants and stabilizers. Such additives may beremoved after the removal of the liquid, by heating for example at atemperature of from 100 to 300° C., in particular from 150 to 250° C.,in an inert atmosphere, for example in nitrogen or argon, or in anoxygen containing atmosphere, for example air or a mixture comprisingoxygen and argon.

As an alternative, or in addition, Group 11 metal may be deposited on atleast a portion of the walls of the process microchannels by vapordeposition techniques known in the art.

A cationic Group 11 metal component may be deposited on at least aportion of the walls of the process microchannels by contacting thewalls with a liquid mixture comprising the cationic Group 11 metalcomponent, and removing a liquid component of the liquid mixture. Areducing agent may be applied prior to, together with or after thedeposition of cationic Group 11 metal component. Typically, the liquidmixture may comprise the cationic Group 11 metal component and areducing agent, in which case removing the liquid and performingreduction of at least a portion of the cationic Group 11 metal componentmay be accomplished simultaneously. Such deposition may be carried outmore than once, for example two times or three times, to accomplish thedeposition of a desired amount of Group 11 metal. The cationic Group 11metal component includes, for example a non-complexed or complexed Group11 metal salt, in particular, a cationic Group 11 metal-amine complex.Contacting the walls with a liquid mixture comprising a cationic Group11 metal-amine complex and a reducing agent may be followed by heatingat a temperature of from 100 to 300° C., in particular from 150 to 250°C., in an inert atmosphere, for example in nitrogen or argon, or in anoxygen containing atmosphere, for example air or a mixture comprisingoxygen and argon. The heating will, in general, effect the reduction ofat least a portion of the cationic Group 11 metal-amine complex.Examples of cationic Group 11 metal-amine complexes are cationic Group11 metal complexed with a monoamine or a diamine, in particular a1,2-alkylene diamine. Examples of suitable amines are ethylene diamine,1,2-propylene diamine, 2,3-butylene diamine, and ethanol amine. Higheramines may be used, such as, for example, triamines, tetraamines, andpentaamines. Examples of reducing agents are oxalates, lactates andformaldehyde. The quantity of Group 11 metal in such liquid mixture maybe in the range of from 1 to 40% w, in particular from 2 to 30% w,calculated as the weight of the Group 11 metal relative to the weight ofthe liquid mixture. For further particulars of liquid mixturescomprising cationic Group 11 metal-amine complex and a reducing agent,reference may be made to U.S. Pat. No. 5,380,697, U.S. Pat. No.5,739,075, EP-A-266015, and U.S. Pat. No. 6,368,998, which areincorporated herein by reference.

In some embodiments, Group 11 metal or cationic Group 111 metalcomponent may be deposited on at least a portion of the walls of theprocess microchannels before the microchannel reactor is manufactured byassembling sheets, as described hereinbefore. In such embodimentsportions of the walls on which no Group 11 metal is to be deposited maybe shielded by a temporary coating. In other embodiments, Group 11 metalor cationic Group 11 metal component may be deposited on at least aportion of the walls of the process microchannels after they have beenformed by assembling the sheets described hereinbefore. In suchembodiments, inserts may be placed temporarily in the sections of themicrochannels where no Group 11 metal is to be deposited on the walls.

In some embodiments, Group 11 metal or cationic Group 11 metal componentmay be deposited on at least a portion of the walls of the processmicrochannels wherein the said walls are at least partly covered with acarrier material, and Group 11 metal or cationic Group 11 metalcomponent is deposited on or in the carrier material, suitably by usingan impregnation method. The said walls may be at least partly coveredwith the carrier material by wash coating, prior to or after assemblingthe process microchannels. Particulars of suitable carrier materials areas specified hereinafter.

In some embodiments, the walls of the process microchannels on whichGroup 11 metal or cationic Group 11 metal component may be deposited areat least partly roughened or corrugated. Roughening or corrugation mayprovide grooves and elevations, so that the roughened or corrugated wallsurface is effectively enlarged, for example, by a factor of from 0.5 to10, or from 1 to 5, relative to the surface area of the roughened orcorrugated wall surface as defined by its outer dimensions. This canincrease the adhesion of the epoxidation catalyst deposited on the wall,and it will effect that more epoxidation catalyst surface can contributein catalyzing the epoxidation reaction. Roughening and corrugation maybe achieved by methods known in the art, for example by etching or byapplying abrasive power.

In some embodiments, the said deposition of Group 11 metal or cationicGroup 11 metal component, with subsequent reduction, will yield a Group11 metal mirror positioned on the walls of the process microchannels,and in other embodiments this will yield discrete Group 11 metalparticles, for example in the form of spheres. In yet other embodiments,a combination of a mirror and discrete particles will be yielded. Suchmorphology differences are not essential in the practice of the presentinvention.

One or more promoter components may be deposited on at least a portionof the same walls of the process microchannels as the walls on whichGroup 11 metal or cationic Group 11 metal component is deposited. Thedeposition of promoter components may be effected prior to, togetherwith or subsequent to the deposition of Group 11 metal or cationic Group11 metal component. Particulars of such promoter components, includingsuitable quantities thereof, are disclosed hereinafter. Suitable methodsof depositing the promoter components may include, for example,contacting the walls with a liquid mixture comprising one or more of thepromoter components to be deposited and a diluent, and removing thediluent while leaving at least a portion of the promoter component(s).In particular in embodiments in which the walls of the processmicrochannels are covered with a carrier materials, the liquid mixturemay be kept in contact with the walls for a period of time beforeremoving the diluent, for example for up to 10 hours, in particular for0.25 to 5 hours, and the temperature may be up to 95° C., in particularin the range of from 10 to 80° C. Suitable liquids typically comprisethe promoter component(s) dissolved or dispersed in an aqueous liquid,for example water or an aqueous organic diluent, such as for example amixture of water and one or more of methanol, ethanol, propanol,isopropanol, acetone or methyl ethyl ketone. The deposition may becarried out more than once, for example two times or three times, toaccomplish the deposition of a desired amount of promoter component.Alternatively, different promoter components may be deposited indifferent deposition steps.

In addition to one or more promoter components, one or more componentscomprising one or more further elements may be deposited on at least aportion of the same walls of the process microchannels as the walls onwhich Group 11 metal or cationic Group 11 metal component is deposited.The deposition of components comprising the further elements may beeffected prior to, together with or subsequent to the deposition ofGroup 11 metal or cationic Group 11 metal component, and prior to,together with or subsequent to the deposition of the promotercomponents. Particulars of the components comprising the furtherelements, including suitable quantities thereof, are disclosedhereinafter. Suitable methods of depositing the components comprisingthe further elements include, for example, contacting the walls with aliquid mixture comprising one or more of the components to be depositedand a diluent, and removing the diluent while leaving at least a portionof the component(s). In particular in embodiments in which the walls ofthe process microchannels are covered with a carrier materials, theliquid mixture may be kept in contact with the walls for a period oftime before removing the diluent, for example for up to 10 hours, inparticular for 0.25 to 5 hours, and the temperature may be up to 95° C.,in particular in the range of from 10 to 80° C. Suitable liquidstypically comprise the component(s) dissolved or dispersed in an aqueousliquid, for example water or an aqueous organic diluent, such as forexample a mixture of water and one or more of methanol, ethanol,propanol, isopropanol, tetrahydrofuran, ethylene glycol, ethylene glycoldimethyl ether, diethylene glycol dimethyl ether, dimethylformamide,acetone or methyl ethyl ketone. The deposition may be carried out morethan once, for example two times or three times, to accomplish thedeposition of a desired amount of the components. Alternatively,different components comprising a further element may be deposited indifferent deposition steps.

In an embodiment, the invention provides a method of installing anepoxidation catalyst in one or more process microchannels of amicrochannel reactor, which method comprises introducing into the one ormore process microchannels a dispersion of the catalyst dispersed in anessentially non-aqueous diluent, and removing the diluent.

The essentially non-aqueous diluent may be a liquid, or it may be in agaseous form. As used herein, for liquid diluents, “essentiallynon-aqueous” means that the water content of the diluent is at most 20%w, in particular at most 10% w, more in particular at most 5% w, forexample at most 2% w, or even at most 1% w, or at most 0.5% w, relativeto the weight of the diluent. In particular, for gaseous diluents,“essentially non-aqueous” means that the diluent as present in theprocess microchannels is above the dew point.

The substantial or complete absence of liquid water in the diluentenables the catalyst to better maintain its integrity duringinstallation, in terms of one or more of its morphology, composition andproperties, than when an aqueous diluent is applied. Suitableessentially non-aqueous liquid diluents include organic diluents, forexample hydrocarbons, halogenated hydrocarbons, alcohols, ketones,ethers, and esters. Suitable alcohols include, for example methanol andethanol. The quantity of catalyst which may be present in the liquiddiluent may be in the range of from 1 to 50% w, in particular from 2 to30% w, relative to the weight of the total of the catalyst and theliquid diluent.

Suitable essentially non-aqueous gaseous phase diluents include, forexample, air, nitrogen, argon and carbon dioxide. The quantity ofcatalyst which may be present in the gaseous phase diluent may be in therange of from 10 to 500 μl, in particular from 22 to 300 g/l, calculatedas the weight of catalyst relative to the volume of the gaseous phasediluent.

The epoxidation catalyst present in the dispersion may be obtained bycrushing a conventional, shaped catalyst and optionally followed bysieving. The particle size of the catalyst present in the dispersion istypically such that d₅₀ is in the range of from 0.1 to 100 μm, inparticular from 0.5 to 50 μm. As used herein, the average particle size,referred to herein as “d₅₀”, is as measured by a Horiba LA900 particlesize analyzer and represents a particle diameter at which there areequal spherical equivalent volumes of particles larger and particlessmaller than the stated average particle size. The method of measurementincludes dispersing the particles by ultrasonic treatment, thus breakingup secondary particles into primary particles. This sonificationtreatment is continued until no further change in the d₅₀ value isnoticed, which typically requires 5 minute sonification when using theHoriba LA900 particle size analyzer. Preferably, the epoxidationcatalyst comprises particles having dimensions such that they pass asieve with openings sized at most 50%, in particular at most 30% of thesmallest dimension of the process microchannel.

Conventional, shaped epoxidation catalysts typically comprise Group 11metal, one or more promoter components and optionally one or morecomponents comprising a further element dispersed on a shaped carriermaterial. Suitable carrier materials, suitable promoter components,suitable components comprising a further element and suitable catalystcompositions in respect of the quantities of Group 11 metal, promotercomponents and components comprising a further element may be asdescribed hereinafter.

Alternatively, and preferably, the catalyst present in the dispersion isprepared in accordance with the invention.

The dispersion of the catalyst may be introduced such that a packedcatalyst bed is formed in the designated section of one or more of theprocess microchannels, or alternatively such that at least a portion ofthe walls of the said sections is covered with the catalyst. In theformer case, prior to introducing the dispersion of the catalyst, asupport device, for example a sieve or a graded particulate material,may have been placed in the downstream portion of the designated sectionof the one or more of the process microchannels, to support the catalystand to prevent it from moving further downstream. In the latter case,the catalyst may be deposited on the walls of the process microchannelsprior to or after assembling the process microchannels, or the catalystmay be present on inserts placed in the designated section of theprocess microchannels.

The total quantity of Group 11 metal present in the first section of theprocess microchannels is not material to the invention, and may beselected within wide ranges. Typically, the total quantity of Group 11metal may be in the range of from 10 to 500 kg/m³, more typically from50 to 400 kg/m³, in particular from 100 to 300 kg/m³ reactor volume,wherein reactor volume is the total volume defined by the crosssectional area and the total length of the portions of the processmicrochannels which is occupied by the epoxidation catalyst, by presenceof a packed bed and/or by the presence of the epoxidation catalyst onthe wall. For the avoidance of doubt, the reactor volume so defined doesnot include portions of the process microchannel which do not compriseepoxidation catalyst. In embodiments of the invention wherein the feedcomprises the olefin and oxygen in a total quantity of at least 50mole-%, the total quantity of Group 11 metal may be in the range of from5 to 250 kg/m³, more typically from 20 to 200 kg/m³, in particular from50 to 150 kg/m³ reactor volume, as defined hereinbefore.

In an embodiment, the invention provides a method of preparing aparticulate epoxidation catalyst, which method comprises depositingGroup 11 metal and one or more promoter components on a particulatecarrier material having a pore size distribution such that pores withdiameters in the range of from 0.2 to 10 μm represent at least 70% ofthe total pore volume.

The carrier materials for use in this invention may be natural orartificial inorganic materials and they may include refractorymaterials, silicon carbide, clays, zeolites, charcoal and alkaline earthmetal carbonates, for example calcium carbonate. Preferred arerefractory materials, such as alumina, magnesia, zirconia and silica.The most preferred material is α-alumina. Typically, the carriermaterial comprises at least 85% w, more typically at least 90% w, inparticular at least 95% w α-alumina, frequently up to 99.9% w α-alumina,relative to the weight of the carrier. Other components of the α-aluminamay comprise, for example, silica, alkali metal components, for examplesodium and/or potassium components, and/or alkaline earth metalcomponents, for example calcium and/or magnesium components.

The surface area of the carrier material may suitably be at least 0.1m²/g, preferably at least 0.3 m²/g, more preferably at least 0.5 m²/g,and in particular at least 0.6 m²/g, relative to the weight of thecarrier; and the surface area may suitably be at most 10 m²/g,preferably at most 5 m²/g, and in particular at most 3 m²/g, relative tothe weight of the carrier. “Surface area” as used herein is understoodto relate to the surface area as determined by the B.E.T. (Brunauer,Emmett and Teller) method as described in Journal of the AmericanChemical Society 60 (1938) pp. 309-316. High surface area carriermaterials, in particular when they are an α-alumina optionallycomprising in addition silica, alkali metal and/or alkaline earth metalcomponents, provide improved performance and stability of operation.

The water absorption of the carrier material is typically in the rangeof from 0.2 to 0.8 g/g, preferably in the range of from 0.3 to 0.7 g/g.A higher water absorption may be in favor in view of a more efficientdeposition of Group 11 metal, promoter components and componentscomprising one or more elements. As used herein, water absorption is asmeasured in accordance with ASTM C20, and water absorption is expressedas the weight of the water that can be absorbed into the pores of thecarrier, relative to the weight of the carrier.

The particulate carrier material may have a pore size distribution suchthat pores with diameters in the range of from 0.2 to 10 μm represent atleast 70% of the total pore volume. Such relatively narrow pore sizedistribution can contribute to one or more of the activity, selectivityand longevity of the catalyst. Longevity may be in respect ofmaintaining the catalyst activity and/or maintaining the selectivity. Asused herein, the pore size distribution and the pore volumes are asmeasured by mercury intrusion to a pressure of 3.0×10⁸ Pa using aMicromeretics Autopore 9200 model (130° contact angle, mercury with asurface tension of 0.473 N/m, and correction for mercury compressionapplied).

Preferably, the pore size distribution is such that the pores withdiameters in the range of from 0.2 to 10 μm represent more than 75%, inparticular more than 80%, more preferably more than 85%, most preferablymore than 90% of the total pore volume. Frequently, the pore sizedistribution is such that the pores with diameters in the range of from0.2 to 10 μm represent less than 99.9%, more frequently less than 99% ofthe total pore volume.

Preferably, the pore size distribution is such that the pores withdiameters in the range of from 0.3 to 10 μm represent more than 75%, inparticular more than 80%, more preferably more than 85%, most preferablymore than 90%, in particular up to 100%, of the pore volume contained inthe pores with diameters in the range of from 0.2 to 10 μm.

Typically, the pore size distribution is such that pores with diametersless than 0.2 μm represent less than 10%, in particular less than 5%, ofthe total pore volume. Frequently, the pores with diameters less than0.2 μm represent more than 0.1%, more frequently more than 0.5% of thetotal pore volume.

Typically, the pore size distribution is such that pores with diametersgreater than 10 μm represent less than 20%, in particular less than 10%,more in particular less than 5%, of the total pore volume. Frequently,the pores with diameters greater than 10 μm represent more than 0.1%, inparticular more than 0.5% of the total pore volume.

Typically, the pores with diameters in the range of from 0.2 to 10 μmprovide a pore volume of at least 0.25 ml/g, in particular at least 0.3ml/g, more in particular at least 0.35 ml/g. Typically, the pores withdiameters in the range of from 0.2 to 10 μm provide a pore volume of atmost 0.8 ml/g, more typically at most 0.7 ml/g, in particular at most0.6 ml/g.

The particulate carrier material has typically a d₅₀ in the range offrom 0.1 to 100 μm, in particular from 0.5 to 50 μm. Preferably, theparticulate carrier material comprises particles having dimensions suchthat they pass an ASTM sieve with openings sized at most 50%, inparticular 30% of the smallest dimension of the process microchannel.

The epoxidation catalyst which comprises one or more Group 11 metalsdispersed on a carrier material exhibits appreciable catalytic activitywhen the Group 11 metal content is at least 10 g/kg, relative to theweight of the catalyst. Preferably, the catalyst comprises Group 11metal in a quantity of from 50 to 500 g/kg, more preferably from 100 to400 g/kg.

The promoter component may comprise one or more elements selected fromrhenium, tungsten, molybdenum, chromium, and mixtures thereof.Preferably the promoter component comprises, as one of its elements,rhenium.

The promoter component may typically be present in the epoxidationcatalyst in a quantity of at least 0.05 mmole/kg, more typically atleast 0.5 mmole/kg, and preferably at least 1 mmole/kg, calculated asthe total quantity of the element (that is rhenium, tungsten, molybdenumand/or chromium) relative to the weight of Group 11 metal. The promotercomponent may be present in a quantity of at most 250 mmole/kg,preferably at most 50 mmole/kg, more preferably at most 25 mmole/kg,calculated as the total quantity of the element relative to the weightof Group 11 metal. The form in which the promoter component may bedeposited is not material to the invention. For example, the promotercomponent may suitably be provided as an oxide or as an oxyanion, forexample, as a rhenate, perrhenate, or tungstate, in salt or acid form.

When the epoxidation catalyst comprises a rhenium containing promotercomponent, rhenium may typically be present in a quantity of at least0.5 mmole/kg, more typically at least 2.5 mmole/kg, and preferably atleast 5 mmole/kg, in particular at least 7.5 mmole/kg, calculated as thequantity of the element relative to the weight of Group 11 metal.Rhenium is typically present in a quantity of at most 25 mmole/kg,preferably at most 15 mmole/kg, more preferably at most 10 mmole/kg, inparticular at most 7.5 mmole/kg, on the same basis.

Further, when the epoxidation catalyst comprises a rhenium containingpromoter component, the catalyst may preferably comprise a rheniumcopromoter, as a further component deposited on the carrier. Suitably,the rhenium copromoter may be selected from components comprising anelement selected from tungsten, chromium, molybdenum, sulfur,phosphorus, boron, and mixtures thereof. Preferably, the rheniumcopromoter is selected from components comprising tungsten, chromium,molybdenum, sulfur, and mixtures thereof. It is particularly preferredthat the rhenium copromoter comprises, as an element, tungsten.

The rhenium copromoter may typically be present in a total quantity ofat least 0.05 mmole/kg, more typically at least 0.5 mmole/kg, andpreferably at least 2.5 mmole/kg, calculated as the element (i.e. thetotal of tungsten, chromium, molybdenum, sulfur, phosphorus and/orboron), relative to the weight of Group 11 metal. The rhenium copromotermay be present in a total quantity of at most 200 mmole/kg, preferablyat most 50 mmole/kg, more preferably at most 25 mmole/kg, on the samebasis. The form in which the rhenium copromoter may be deposited is notmaterial to the invention. For example, it may suitably be provided asan oxide or as an oxyanion, for example, as a sulfate, borate ormolybdate, in salt or acid form.

The epoxidation catalyst preferably comprises Group 11 metal, thepromoter component, and a component comprising a further element.Eligible further elements may be selected from the group of nitrogen,fluorine, alkali metals, alkaline earth metals, titanium, hafnium,zirconium, vanadium, thallium, thorium, tantalum, niobium, gallium andgermanium and mixtures thereof. Preferably the alkali metals areselected from lithium, potassium, rubidium and cesium. Most preferablythe alkali metal is lithium, potassium and/or cesium. Preferably thealkaline earth metals are selected from calcium and barium. Typically,the further element is present in the epoxidation catalyst in a totalquantity of from 0.05 to 2500 mmole/kg, more typically from 0.25 to 500mmole/kg, calculated as the element on the weight of Group 11 metal. Thefurther elements may be provided in any form. For example, salts of analkali metal or an alkaline earth metal are suitable.

As used herein, the quantity of alkali metal present in the epoxidationcatalyst is deemed to be the quantity insofar as it can be extractedfrom the epoxidation catalyst with de-ionized water at 100° C. Theextraction method involves extracting a 10-gram sample of the catalystthree times by heating it in 20 ml portions of de-ionized water for 5minutes at 100° C. and determining in the combined extracts the relevantmetals by using a known method, for example atomic absorptionspectroscopy.

As used herein, the quantity of alkaline earth metal present in theepoxidation catalyst is deemed to the quantity insofar as it can beextracted from the epoxidation catalyst with 10% w nitric acid inde-ionized water at 100° C. The extraction method involves extracting a10-gram sample of the catalyst by boiling it with a 100 ml portion of10% w nitric acid for 30 minutes (1 atm., i.e. 101.3 kPa) anddetermining in the combined extracts the relevant metals by using aknown method, for example atomic absorption spectroscopy. Reference ismade to U.S. Pat. No. 5,801,259, which is incorporated herein byreference.

Methods for depositing Group 11 metal, the one or more promotercomponents and the one or more component comprising a further element ona carrier material are known in the art and such methods may be appliedin the practice of this invention. Reference may be made to U.S. Pat.No. 5,380,697, U.S. Pat. No. 5,739,075, EP-A-266015, and U.S. Pat. No.6,368,998, which are incorporated herein by reference. Suitably, themethods include impregnating the particulate carrier materials with aliquid mixture comprising cationic Group 11 metal-amine complex and areducing agent.

In some embodiments, the invention provides processes for theepoxidation of an olefin comprising reacting a feed comprising theolefin and oxygen in the presence an epoxidation catalyst, as describedhereinbefore, contained in one or more process microchannels of amicrochannel reactor.

The olefin for use in the present invention may be an aromatic olefin,for example styrene, or a di-olefin, whether conjugated or not, forexample 1,9-decadiene or 1,3-butadiene. A mixture of olefins may beused. Typically, the olefin is a monoolefin, for example 2-butene orisobutene. Preferably, the olefin is a mono-α-olefin, for example1-butene or propylene. The most preferred olefin is ethylene.

The feed for the epoxidation process of this invention comprises theolefin and oxygen. As used herein, the feed to a process is understoodto represent the total of reactants and other components which is fed tothe section of the process microchannels in which the process inquestion takes place. Some of the feed components may be fed to theepoxidation process through an opening in upstream end 220 of processmicrochannels 210. Some of the feed components may be fed through firstfeed channel 260 and one or more first orifices 280. For example, anolefin rich feed component may be fed through the opening in theupstream end of the process microchannels and an oxygen rich feedcomponent may be fed through the first feed channel and the one or morefirst orifices. Alternatively, the oxygen rich feed component may be fedthrough the opening in the upstream end of the process microchannels andthe olefin rich feed component may be fed through the first feed channeland the one or more first orifices. Certain feed components may be fedthrough the opening in the upstream end of the process microchannels andthrough the first feed channel and the one or more first orifices. Forexample, the olefin may be fed partly through the opening in theupstream end of the process microchannels and partly through the firstfeed channel and the one or more first orifices. As another example,oxygen may be fed partly through the opening in the upstream end of theprocess microchannels and partly through the first feed channel and theone or more first orifices.

In an embodiment, an oxygen rich feed component may be contacted withinthe process microchannels with an olefin rich feed component. The oxygenrich feed component is typically relatively lean in the olefin. Theoxygen rich feed component may comprise oxygen typically in a quantityof at least 5 mole-%, in particular at least 10 mole-%, more inparticular at least 15 mole-%, relative to the total oxygen rich feedcomponent, and typically in a quantity of at most 100 mole-%, or at most99.9 mole-%, or at most 99.8 mole-%, relative to the total oxygen richfeed component. The oxygen rich feed component may comprise the olefintypically in a quantity of at most 5 mole-%, in particular at most 1mole-%, relative to the total oxygen rich feed component. Such oxygenrich feed component may normally be outside the explosion limits. Theolefin rich feed component is typically relatively lean in oxygen. Theolefin rich feed component may comprise the olefin typically in aquantity of at least 20 mole-%, in particular at least 25 mole-%, morein particular at least 30 mole-%, relative to the total olefin rich feedcomponent, and typically in a quantity of at most 100 mole-%, or at most99.99 mole-%, or at most 99.98 mole-%, relative to the total olefin richfeed component. The olefin rich feed component may comprise oxygentypically in a quantity of at most 15 mole-%, in particular at most 10mole-%, more in particular at most 5 mole-%, relative to the totalolefin rich feed component. Such olefin rich feed component may normallybe outside the explosion limits.

In the case that there is a plurality of first orifices 280, one or morefirst orifices 280 positioned downstream of another first orifice 280,converted reactant may be substantially replenished. For example,replenishing converted oxygen may effect that the concentration ofoxygen in the feed can be maintained substantially constant along thelength of the epoxidation catalyst, which may favor substantiallycomplete conversion of the olefin. Alternatively, the concentration ofthe olefin may be kept substantially constant by replenishing convertedolefin, which may favor substantially complete conversion of oxygen.

Further, in an aspect of the invention, by feeding the olefin rich feedcomponent and the oxygen rich feed component through different channelsand mixing the feed components in the process microchannels effects,feed compositions can be accomplished within the process microchannels,while outside the process microchannels such feed compositions couldlead to an explosion.

An organic halide may be present in the feed as a reaction modifier forincreasing the selectivity, suppressing the undesirable oxidation of theolefin or the olefin oxide to carbon dioxide and water, relative to thedesired formation of the olefin oxide. The organic halide may be fed asa liquid or as a vapor. The organic halide may be fed separately ortogether with other feed components through an opening in upstream end220 of the process microchannels 210 or through first feed channel 260and one or more first orifices 280. An aspect of feeding the organichalide through a plurality first orifices is that there may be anincrease in the level of the quantity of the organic halide along thelength of the epoxidation catalyst, by which the activity and/orselectivity of the epoxidation catalyst can be manipulated in accordancewith the teachings of EP-A-352850, which is incorporated herein byreference. For example, when using a rhenium containing epoxidationcatalyst, the activity of the epoxidation catalyst can be enhanced alongthe length of the epoxidation catalyst. This could allow for betterutilization of the epoxidation catalyst in regions where oxygen or theolefin is depleted relative to the regions where oxygen and the olefinare fed.

Organic halides are in particular organic bromides, and more inparticular organic chlorides. Preferred organic halides arechlorohydrocarbons or bromohydrocarbons. More preferably they areselected from the group of methyl chloride, ethyl chloride, ethylenedichloride, ethylene dibromide, vinyl chloride or a mixture thereof.Most preferred are ethyl chloride and ethylene dichloride.

In addition to an organic halide, an organic or inorganic nitrogencompound may be employed as reaction modifier, but this is generallyless preferred. It is considered that under the operating conditions ofthe epoxidation process the nitrogen containing reaction modifiers areprecursors of nitrates or nitrites (cf. e.g. EP-A-3642 and U.S. Pat. No.4,822,900, which are incorporated herein by reference). Organic nitrogencompounds and inorganic nitrogen compounds may be employed. Suitableorganic nitrogen compounds are nitro compounds, nitroso compounds,amines, nitrates and nitrites, for example nitromethane, 1-nitropropaneor 2-nitropropane. Suitable inorganic nitrogen compounds are, forexample, nitrogen oxides, hydrazine, hydroxylamine or ammonia. Suitablenitrogen oxides are of the general formula NO_(x) wherein x is in therange of from 1 to 2, and include for example NO, N₂O₃ and N₂O₄.

The organic halides and the organic or inorganic nitrogen compounds aregenerally effective as reaction modifier when used in low totalconcentration, for example up to 0.01 mole-%, relative to the totalfeed. It is preferred that the organic halide is present at aconcentration of at most 50×10⁻⁴ mole-%, in particular at most 20×10⁻⁴mole-%, more in particular at most 15×10⁻⁴ mole-%, relative to the totalfeed, and preferably at least 0.2×10⁻⁴ mole-%, in particular at least0.5×10⁻⁴ mole-%, more in particular at least 1×10⁻⁴ mole-%, relative tothe total feed.

In addition to the olefin, oxygen and the organic halide, the feed mayadditionally comprise one or more further components, for examplesaturated hydrocarbons, as ballast gas, inert gases and carbon dioxide.The one or more further components may be fed separately or togetherwith other feed components through an opening in upstream end 220 of theprocess microchannels 210 or through first feed channel 260 and one ormore first orifices 280.

The olefin concentration in the feed may be selected within a widerange. Typically, the olefin concentration in the feed will be at most80 mole-%, relative to the total feed. Preferably, it will be in therange of from 0.5 to 70 mole-%, in particular from 1 to 60 mole-%, onthe same basis.

The oxygen concentration in the feed may be selected within a widerange. Typically, the concentration of oxygen applied will be within therange of from 1 to 15 mole-%, more typically from 2 to 12 mole-% of thetotal feed.

The saturated hydrocarbons comprise, for example, methane and ethane.Unless stated herein otherwise, saturated hydrocarbons may be present ina quantity of up to 80 mole-%, in particular up to 75 mole-%, relativeto the total feed, and frequently they are present in a quantity of atleast 30 mole-%, more frequently at least 40 mole-%, on the same basis.

Carbon dioxide may be present in the feed as it is formed as a result ofundesirable oxidation of the olefin and/or the olefin oxide, and it mayaccordingly be present in feed components present in a recycle stream.Carbon dioxide generally has an adverse effect on the catalyst activity.Advantageously, the quantity of carbon dioxide is, for example, below 2mole-%, preferably below 1 mole-%, or in the range of from 0.2 to 1mole-%, relative to the total feed.

The inert gases include, for example nitrogen or argon. Unless statedherein otherwise, the inert gases may be present in the feed in aconcentration of from 30 to 90 mole-%, typically from 40 to 80 mole-%.

The epoxidation process of this invention may be air-based oroxygen-based, see “Kirk-Othmer Encyclopedia of Chemical Technology”,3^(rd) edition, Volume 9, 1980, pp. 445-447. In the air-based processair or air enriched with oxygen is employed as the source of theoxidizing agent while in the oxygen-based processes high-purity (atleast 95 mole-%) oxygen is employed as the source of the oxidizingagent. Presently most epoxidation plants are oxygen-based and this ispreferred in the practice of certain embodiment of this invention. It isan advantage of other embodiments of this invention that air may be fedto the process as the source of the oxidizing agent.

The epoxidation process may be carried out using reaction temperaturesselected from a wide range. Preferably the reaction temperature is inthe range of from 150 to 340° C., more preferably in the range of from180 to 325° C. Typically, the heat transfer liquid present in the firstheat exchange channels may have a temperature which is typically 0.5 to10° C. lower than the reaction temperature.

As disclosed herein before, during use, the epoxidation catalysts may besubject to a performance decline. In order to reduce effects of anactivity decline, the reaction temperature may be increased gradually orin a plurality of steps, for example in steps of from 0.1 to 20° C., inparticular 0.2 to 10° C., more in particular 0.5 to 5° C. The totalincrease in the reaction temperature may be in the range of from 10 to140° C., more typically from 20 to 100° C. The reaction temperature maybe increased typically from a level in the range of from 150 to 300° C.,more typically from 200 to 280° C., when a fresh epoxidation catalyst orrejuvenated epoxidation catalyst is used, to a level in the range offrom 230 to 340° C., more typically from 240 to 325° C., when theepoxidation catalyst has decreased in activity.

The epoxidation process is preferably carried out at a pressure, asmeasured at upstream 220 end of the process microchannels 210, in therange of from 1000 to 3500 kPa.

The olefin oxide leaving the section of the process microchannelscontaining the epoxidation catalyst is comprised in a reaction mixturewhich may further comprise unreacted olefin, unreacted oxygen, and otherreaction products such as carbon dioxide. Typically, the content ofolefin oxide in the reaction product is in general in the range of from1 to 25 mole-%, more typically from 2 to 20 mole-%, in particular from 2to 5 mole-%.

In an embodiment, the invention provides a process for the epoxidationof an olefin comprising reacting a feed comprising the olefin and oxygenin a total quantity of at least 50 mole-%, relative to the total feed,in the presence an epoxidation catalyst contained in one or more processmicrochannels of a microchannel reactor. In this embodiment, the olefinand oxygen may be present in the feed in a total quantity of at least 80mole-%, in particular at least 90 mole-%, more in particular at least 95mole-%, relative to the total feed, and typically up to 99.5 mole-%, inparticular up to 99 mole-%, relative to the total feed. The molar ratioof olefin to oxygen may be in the range of from 3 to 100, in particularfrom 4 to 50, more in particular from 5 to 20. The saturatedhydrocarbons and the inert gases may be substantially absent. As usedherein, in this context “substantially absent” means that the quantityof saturated hydrocarbons in the feed is at most 10 mole-%, inparticular at most 5 mole-%, more in particular at most 2 mole-%,relative to the total feed, and that the quantity of inert gases in thefeed is at most 10 mole-%, in particular at most 5 mole-%, more inparticular at most 2 mole-%, relative to the total feed. In thisparticular embodiment, process conditions may be applied such that thequantity of olefin oxide in the epoxidation reaction mixture is in therange of from 4 to 15 mole-%, in particular from 5 to 12 mole-%, forexample from 6 to 10 mole-%. Preferably, the epoxidation reactionmixture, including the olefin oxide, is quenched, as described herein.

In an embodiment, the invention provides a process for the epoxidationof an olefin comprising reacting a feed comprising the olefin and oxygenin the presence an epoxidation catalyst contained in one or more processmicrochannels of a microchannel reactor, and applying conditions forreacting the feed such that the conversion of the olefin or theconversion of oxygen is at least 90 mole-%. The conversion of the olefinmay be at least 90 mole-% and the conversion of oxygen may be at least90 mole-%. In particular, in this embodiment, the feed may comprise theolefin and oxygen in a quantity of at most 50 mole-%, relative to thetotal feed, and the feed may additionally comprise saturatedhydrocarbons, as ballast gas, and inert gas. Typically, processconditions are applied such that the conversion of the olefin or theconversion of oxygen is at least 95 mole-%, in particular at least 98mole-%, more in particular at least 99 mole-%. As used herein, theconversion is the quantity of a reactant converted relative to thequantity of the reactant in the feed, expressed in mole-%. Preferably,the conversion of the olefin is at least 95 mole-%, in particular atleast 98 mole-%, more in particular at least 99 mole-% and oxygen may beat least partly replenished. The presence of an excess of oxygen in thefeed, relative to the olefin, assists in achieving a high conversion ofthe olefin. For example, the molar ratio of oxygen over the olefin inthe feed may be at least 1.01, typically at least 1.05, in particular atleast 1.1, more in particular at least 1.2; and for example at most 5,in particular at most 3, more in particular at most 2. In thisembodiment, a relatively high selectivity in the conversion of theolefin into the olefin oxide is achieved. A used herein, the selectivityis the quantity of olefin oxide formed, relative to the quantity ofolefin converted, expressed in mole-%. Moreover, such high conversion ofthe olefin enables that the process may be carried out economically in aonce-through mode, which means that no recycle of unconverted reactantsis applied, and that air may be fed to the epoxidation process, whichmeans effectively that the need of an air separation unit is eliminated.

In the practice of this invention, the reaction product, including theolefin oxide, may be quenched by heat exchange with a heat exchangefluid. The quenching may be conducted in second section 340 of processmicrochannels 210 by heat exchange with heat exchange fluid present inone or more second heat exchange channels 350. Typically, thetemperature of the reaction product, including the olefin oxide, may bedecreased to a temperature of at most 250° C., more typically at most225° C., preferably in the range of from 20 to 200° C., more preferably50 to 190° C., in particular from 80 to 180° C. The quenching may resultin a reduction in temperature in the range of from 50 to 200° C., inparticular from 70 to 160° C. Quenching enables increasing the totalquantity of the olefin oxide and oxygen in the feed of the epoxidationprocess, and eliminating the ballast gas or reducing the quantity ofballast gas in the feed of the epoxidation process. Also, a result ofquenching is that the olefin oxide produced is a cleaner product,comprising less aldehyde and carboxylic acid impurities.

In some embodiments, the invention provides a process for theepoxidation of an olefin comprising

reacting a feed comprising an olefin and oxygen in the presence of anepoxidation catalyst to thereby form a first mixture comprising theolefin oxide and carbon dioxide, as described hereinbefore,

quenching the first mixture, typically by heat exchange with a heatexchange fluid or by mixing with a fluid, and

converting the quenched first mixture to form a second mixturecomprising the olefin oxide and a 1,2-carbonate. An advantage of theprocesses in accordance with these particular embodiments is that areduction is achieved in the complexity of the handling of productstreams and recycle streams, compared to the handling of such streams ina conventional olefin epoxidation process, because it eliminates theneed for, for example, an olefin oxide recovering unit and a carbondioxide removal unit. Reaction conditions and types of catalysts asdescribed herein may be employed, on the understanding that thecatalysts may be in particulate form or in the form of well known,shaped bodies. Without compromising these advantages, a reactor otherthan a microchannel reactor may be employed, and the steps of theprocess may be performed in more than one piece of equipment. Forexample, one or more microchannel reactors, shell-and-tube heatexchanger reactors, stirred tank reactors, bubble columns orcondensation apparatus may be employed instead of, or in addition to, amicrochannel reactor. The present invention therefore encompasses theuse of such other types of reactors or condensation apparatus, or theuse of a plurality of reactors or condensation apparatus in theseprocesses. On the other hand, there is a preference to benefitadditionally from the advantages of employing in these processes amicrochannel reactor having process microchannels, as described herein.Therefore, preferably, the invention provides a process for theepoxidation of an olefin comprising

reacting a feed comprising an olefin and oxygen in the presence of anepoxidation catalyst contained in a first section 240 of one or moreprocess microchannels 210 of a microchannel reactor to thereby form afirst mixture comprising the olefin oxide and carbon dioxide, asdescribed hereinbefore,

quenching the first mixture in intermediate section 440 of the one ormore process microchannels 210 positioned downstream of first section240 by heat exchange with a heat exchange fluid, in a same manner asdescribed hereinbefore, and

converting in second section 340 of the one or more processmicrochannels 210 positioned downstream of intermediate section 440 thequenched first mixture to form a second mixture comprising the olefinoxide and a 1,2-carbonate.

The conversion of the quenched first mixture comprising the olefin oxideand carbon dioxide to form the second mixture comprising the olefinoxide and a 1,2-carbonate typically involves reacting at least a portionof the olefin oxide present in the first mixture with at least a portionof the carbon dioxide present in the first mixture to form the1,2-carbonate. Typically, carbon dioxide present in the first mixture iscarbon dioxide co-formed in the epoxidation reaction. The molar quantityof carbon dioxide present in the first mixture may be in the range offrom 0.01 to 1 mole, in particular 0.02 to 0.8 mole, more in particular0.05 to 0.6 mole-%, per mole of the olefin oxide present in the firstmixture. Reaction conditions, catalysts and further methods suitable forthe conversion of the olefin oxide with carbon dioxide are as disclosedhereinafter. Typically, at least 50 mole-%, in particular at least 80mole-%, more in particular at least 90 mole-% of the carbon dioxide isconverted, for example at least 98 mole-%, and in the practice of thisinvention, frequently at most 99.9 mole-% is converted. Additionalcarbon dioxide may be fed to the second section, but that is frequentlynot a preferred embodiment.

In this embodiment, in cases that the second mixture is formed as agaseous phase, the process may additionally comprise condensing at leasta portion of the second mixture comprising the olefin oxide and the1,2-carbonate in a third section of the one or more processmicrochannels, which third section is positioned downstream of thesecond section. Typically, condensing at least a portion of the secondmixture involves removal of heat by heat exchange with a heat exchangefluid. Such heat exchange fluid may be present in a fourth heat exchangechannel, as described hereinbefore. Typically, at least 50 mole-%, inparticular at least 80 mole-%, more in particular at least 90 mole-% ofthe total of the olefin oxide and the 1,2-carbonate present in thesecond mixture is condensed, for example at least 98 mole-%, and in thepractice of this invention, frequently at most 99.9 mole-% is condensed.Preferably, in cases that the second mixture comprises water at leastpartly as a gaseous phase, the process may additionally comprisecondensing at least a portion of such water present in the secondmixture in the third section. Typically, water present in the secondmixture, if any, is water co-formed in the epoxidation reaction. Themolar quantity of water present in the second mixture may be in therange of from 0.01 to 1 mole, in particular 0.02 to 0.8 mole, more inparticular 0.05 to 0.6 mole-%, per mole of the total quantities of theolefin oxide and the 1,2-carbonate present in the second mixture.Typically, at least 50 mole-%, in particular at least 80 mole-%, more inparticular at least 90 mole-% of the total of the water present in thesecond mixture is condensed, for example at least 98 mole-%, and in thepractice of this invention, frequently at most 99.9 mole-% is condensed.

As described hereinbefore, during the operation of the epoxidationprocess, the epoxidation catalyst is subject to a performance decline.The epoxidation catalyst may be removed from the process microchannel byblowing with a suitable gas, for example, air, nitrogen, argon or carbondioxide, either in the normal downstream direction, or in backflow. Asupport device, if applied, may be removed from the processmicrochannels, prior to removing the epoxidation catalyst.

In accordance with an embodiment of the invention, the epoxidationcatalyst may be rejuvenated by a method which comprises washing thecatalyst with an aqueous liquid, and depositing one or more promotercomponents on the washed catalyst.

The aqueous liquid which may be used in rejuvenating the epoxidationcatalyst may be, for example water or an aqueous organic diluent, suchas for example, a mixture of water and methanol ethanol, propanol,isopropanol, tetrahydrofuran, ethylene glycol, ethylene glycol dimethylether, diethylene glycol dimethyl ether, dimethylformamide, acetone, ormethyl ethyl ketone. Washing may be carried out at an elevatedtemperature, for example at a temperature from 30 to 100° C., or 35 to95° C. The washing may comprise contacting the epoxidation catalyst withthe aqueous liquid for a period of time, for example up to 10 hours, inparticular from 0.25 to 5 hours, and removing the liquid together withmaterials leached form the epoxidation catalyst into the liquid. Thewashing may be repeated, for example two or three times, until there isno change in the composition of the effluent. The effluent may betreated and/or separated and/or purified, such that the any Group 11metal and any promoter components present in the effluent may be reused,as a promoter component, or for any other use. For example, rhenium, ifpresent as a promoter component, may be recovered from the effluent as aperrhenate, or as the corresponding acid, by separation methodsinvolving exchange resins.

The one or more promoter components may be deposited on the washedcatalyst by the methods described hereinbefore. The one or more promotercomponents and their quantities may be as described hereinbefore. Inaddition to one or more promoter components, one or more componentscomprising one or more further elements may be deposited on the washedcatalyst prior to, together with or subsequent to the deposition of thepromoter components, by using any of the methods described hereinbefore.Particulars of the components comprising the further elements, includingsuitable quantities thereof, are disclosed hereinafter. If desirable, inaddition to one or more promoter components, Group 11 metal may bedeposited on the washed carrier, by using any of the methods describedhereinbefore, in order to adjust the desired quantity of Group 11 metalcontent of the epoxidation catalyst, or to compensate for a loss ofGroup 11 metal. After completing the rejuvenation, a feed comprising theolefin and oxygen may be reacted in the presence of the rejuvenatedcatalyst, according to the methods described hereinbefore.

The inventive method of rejuvenating the epoxidation catalyst is inparticular directed to restoring at least partly the performance level,in particular activity and/or selectivity, which the epoxidationcatalyst had before it was used in an epoxidation process. The inventivemethod of rejuvenating the epoxidation catalyst may be applied after theepoxidation catalyst has been used again following an earlierrejuvenation.

The inventive method of rejuvenating an epoxidation catalyst may beapplicable with the epoxidation catalyst present in any reactor suitablefor the epoxidation of an olefin. Examples of such reactors are reactorsin the form of shell-and-tube heat exchangers and microchannel reactors.It is an advantageous aspect of the invention that during therejuvenation the epoxidation catalyst may be present in the epoxidationreactor, in particular in the reaction tubes of the shell-and-tube heatexchanger reactor, which eliminates the need of removing the epoxidationfrom the epoxidation reactor and the catalyst may stay in place afterthe rejuvenation for use during a further period of production of theolefin oxide from the olefin and oxygen. In particular, it is anadvantageous aspect of this invention that during the rejuvenation theepoxidation catalyst may be present in the first section of the one ormore process microchannels and may stay there after the rejuvenation foruse during a further period of production of the olefin oxide from theolefin and oxygen.

The epoxidation reaction mixture, including the olefin oxide, may bewithdrawn from the process microchannel and the microchannel reactor andbe processed in the conventional manner, using conventional methods andconventional equipment. A separation system may provide for theseparation of the olefin oxide from any unconverted olefin, anyunconverted oxygen, any ballast gas and carbon dioxide. An aqueousextraction fluid such as water may be used to separate these components.The enriched extraction fluid containing the olefin oxide may be furtherprocessed for recovery of the olefin oxide. The olefin oxide producedmay be recovered from the enriched extraction fluid, for example bydistillation or extraction. A mixture which comprises any unconvertedolefin, any unconverted oxygen, any ballast gas and carbon dioxide andwhich is lean in olefin oxide may be extracted to at least partly removecarbon dioxide. The resulting carbon dioxide lean mixture may berecompressed, dried and recycled as a feed component to the epoxidationprocess of this invention.

The olefin oxide produced in the epoxidation process of the inventionmay be converted by conventional methods into a 1,2-diol, a 1,2-diolether, a 1,2-carbonate or an alkanol amine.

The conversion into the 1,2-diol or the 1,2-diol ether may comprise, forexample, reacting the ethylene oxide with water, in a thermal process orby using a catalyst, which may be an acidic catalyst or a basiccatalyst. For example, for making predominantly the 1,2-diol and less1,2-diol ether, the olefin oxide may be reacted with a ten fold molarexcess of water, in a liquid phase reaction in presence of an acidcatalyst, e.g. 0.5-1.0% w sulfuric acid, based on the total reactionmixture, at 50-70° C. at 100 kPa absolute, or in a gas phase reaction at130-240° C. and 2000-4000 kPa absolute, preferably in the absence of acatalyst. The presence of such a large quantity of water may favor theselective formation of 1,2-diol and may function as a sink for thereaction exotherm, helping controlling the reaction temperature. If theproportion of water is lowered the proportion of 1,2-diol ethers in thereaction mixture is increased. The 1,2-diol ethers thus produced may bea di-ether, tri-ether, tetra-ether or a subsequent ether. Alternative1,2-diol ethers may be prepared by converting the olefin oxide with analcohol, in particular a primary alcohol, such as methanol or ethanol,by replacing at least a portion of the water by the alcohol.

The olefin oxide may be converted into the corresponding 1,2-carbonateby reacting it with carbon dioxide. If desired, a 1,2-diol may beprepared by subsequently reacting the 1,2-carbonate with water or analcohol to form the 1,2-diol. For applicable methods, reference is madeto U.S. Pat. No. 6,080,897, which is incorporated herein by reference.

The conversion into the alkanol amine may comprise reacting the olefinoxide with an amine, such as ammonia, an alkyl amine or a dialkyl amine.Anhydrous or aqueous ammonia may be used. Anhydrous ammonia is typicallyused to favor the production of mono alkanol amine. For methodsapplicable in the conversion of the olefin oxide into the alkanol amine,reference may be made to, for example U.S. Pat. No. 4,845,296, which isincorporated herein by reference.

In an embodiment, the invention provides a process for the preparationof a 1,2-diol, a 1,2-diol ether, a 1,2-carbonate or an alkanol amine,which process comprises

reacting a feed comprising an olefin and oxygen in the presence anepoxidation catalyst contained in a first section of one or more processmicrochannels of a microchannel reactor, which may be accomplished asdescribed hereinbefore, and

converting the olefin oxide with water, an alcohol, carbon dioxide or anamine to form the 1,2-diol, 1,2-diol ether, 1,2-carbonate or alkanolamine in a second section of the one or more process microchannelspositioned downstream of the first section.

The invention also provides a reactor which is suitable for theinventive process for the preparation of a 1,2-diol, a 1,2-diol ether, a1,2-carbonate or an alkanol amine. Accordingly, an embodiment of theinvention provides a reactor suitable for the preparation of a 1,2-diol,a 1,2-diol ether or an alkanol amine, which reactor is a microchannelreactor comprising

one or more process microchannels comprising

an upstream end,

a downstream end,

a first section, as described hereinbefore, which is adapted to nepoxidation catalyst, to receive a feed comprising an olefin and oxygen,and to cause conversion of at least a portion of the feed to form anolefin oxide in the presence of the epoxidation catalyst, and

a second section positioned downstream of the first section which isadapted to receive the olefin oxide; to receive water, an alcohol,carbon dioxide or an amine; and to cause conversion of the olefin oxideto form the 1,2-diol, 1,2-diol ether, 1,2-carbonate or alkanol amine.

The conversion of the olefin oxide with water, an alcohol, carbondioxide or an amine in the second section of the one or more processmicrochannels may be a thermal conversion, or a conversion which iscatalyzed by using a suitable catalyst. Suitable catalysts are, forexample, acid catalysts and basic catalysts. Acidic catalysts are, forexample, strongly acid ion exchange resins, such as, for example, thosecomprising sulfonic acid groups on a styrene/divinylbenzene copolymermatrix. Other suitable acid catalysts are, for example, silicas andoxides of metals selected from Groups 3-6 of the Periodic Table of theElements, for example, zirconium oxide and titanium oxide. Basiccatalysts are, for example, strong basic ion exchange resins such as,for example, those comprising quaternary phosphonium or quaternaryammonium groups on a styrene/divinylbenzene copolymer matrix. Suchcatalysts are known in the art, for example from EP-A-156449, U.S. Pat.No. 4,982,021, U.S. Pat. No. 5,488,184. U.S. Pat. No. 6,153,801 and U.S.Pat. No. 6,124,508, which are incorporated herein by reference, and/orthey are commercially available. Suitable catalysts may representthemselves as a liquid under the conditions of the reaction, for examplemineral acids, such as, for example, sulfuric acid and phosphoric acid,and such catalysts as known from JP-A-56-092228, which is incorporatedherein by reference.

Suitable catalysts for the conversion of the olefin oxide with carbondioxide may be, for example, resins which comprise quaternaryphosphonium halide groups or quaternary ammonium halide groups on astyrene/divinylbenzene copolymer matrix, wherein the halide may be inparticular chloride or bromide. Such catalysts for this conversion areknown from T. Nishikubo, A. Kameyama, J. Yamashita and M. Tomoi, Journalof Polymer Science, Pt. A. Polymer Chemist, 31, 939-947 (1993), which isincorporated herein by reference. More suitable catalysts comprise ametal salt immobilized in a solid carrier, wherein the metal salt maycomprise a cation of a metal selected from those in the third Period andGroup 2, the fourth Period and Groups 2 and 4-12, the fifth Period andGroups 2, 4-7, 12 and 14, and the sixth Period and Groups 2 and 4-6, ofthe Periodic Table of the Elements, and wherein the carrier contains aquaternary ammonium, quaternary phosphonium, quaternary arsenonium,quaternary stibonium or a quaternary sulfonium cation, which cation maybe separated from the backbone of the carrier by a spacer group of thegeneral formula —(CH₂—O—)_(m)—(CH₂)_(n)—, m and n being integers, withfor example n being at most 10, for example 1, 2, 3 or 6, when m is 0,and n being from 1 to 8, for example 2 or 4, when m is 1. The metal saltmay be selected in particular from the halides, acetates, laureates,nitrates and sulfates of one or more selected from magnesium, calcium,zinc, cobalt, nickel, manganese, copper and tin, for example zincbromide, zinc iodide, zinc acetate, or cobalt bromide. The solid carrierfor immobilizing the metal salt may be, for example silica, asilica-alumina, or a zeolite, or it may be a resin with apolystyrene/divinylbenzene copolymer backbone, or a silica-basedpolymeric backbone, such as in polysiloxanes, or a resin incorporatingquaternized vinylpyridine monomers. Other suitable catalysts for theconversion of the olefin oxide with carbon dioxide are, for example,quaternary phosphonium halides, quaternary ammonium halides, and certainmetal halides. An example is methyltributylphosphonium iodide. Moresuitably, the catalysts comprise an organic base neutralized with ahydrogen halide, wherein the organic base has a pK_(a) greater than 8and comprises a carbon-based compound containing one or more nitrogenand/or phosphorus atoms with at least one free electron pair. Thehydrogen halide may be hydrogen bromide or hydrogen iodide. Examples ofsuch organic bases having a pK_(a) greater than 8 are2-tert-butylimino-2-diethylamino-1,3-dimethylperhydro-1,3,2-diazaphosphorin,as such or on polystyrene, 1,1,3,3-tetramethylguanidine, andtriethanolamine. In this context, the term “neutralized” means that theorganic base and the hydrogen halide have reacted in amounts relative toeach other such that an aqueous solution of the reaction product wouldbe essentially neutral, i.e. having a pH between 6 and 8.

Another suitable catalyst for the conversion of the olefin oxide withcarbon dioxide comprises from 10 to 90 mole-%, based on the mixture, ofan organic base and from 10 to 90 mole-%, based on the mixture, of thesalt of the organic base and a hydrogen halide, wherein the organic basecomprises a carbon-based compound containing one or more nitrogen and/orphosphorus atoms with at least one free electron pair, and has a pK_(a)high enough that it is capable of binding carbon dioxide under thereaction conditions. The hydrogen halide may be hydrogen bromide orhydrogen iodide. Examples of such organic bases having capability ofbinding carbon dioxide are2-tert-butylimino-2-diethylamino-1,3-dimethylperhydro-1,3,2-diazaphosphorin,as such or on polystyrene, 1,1,3,3-tetramethylguanidine, andtriethanolamine. An exemplary catalyst may be based upon1,1,3,3-tetramethylguanidine, hydrogen iodide and molybdenum trioxide ina mole ratio of about 6.6:4.71:1. When using these catalysts in thepresence of water and carbon dioxide, the formed 1,2-carbonate may be atleast partly converted in situ to the corresponding 1,2-glycol.

The catalyst, when present as a solid material under the condition ofthe reaction, may be installed in the second section of the one or moreprocess microchannels by known methods and applicable methods include,for example, filling at least a portion of the second section to form apacked bed, or covering at least a portion of the walls of the secondsection with the catalyst, for example by wash coating. Some of themethods related to the installation of an epoxidation catalyst, as setout hereinbefore, may be applicable to these catalysts in an analogousmanner. The use of a catalyst which is present as a solid material underthe condition of the reaction is less preferred. In embodiments in whichthe catalyst represents itself as a liquid under the conditions of thereaction, the catalyst may be fed to the second section of the one ormore process microchannels through the second feed channel and the oneor more second orifices, suitably together with feed comprising water,the alcohol, carbon dioxide and/or the amine. When the conversion is athermal conversion, the temperature may be in the range of from 100 to300° C., in particular from 150 to 250° C. When the conversion is acatalytic conversion, the temperature may be in the range of from 30 to200° C., in particular from 50 to 150° C. The molar ratio of the totalof water, the alcohol, carbon dioxide and the amine to the olefin oxidemay be more than 10, for example at most 20 or at most 30. However, asdescribed hereinbefore, it is a benefit of this invention that adequatecontrol of the temperature can be achieved when the molar ratio of thetotal of water, the alcohol, carbon dioxide and the amine is keptrelatively low, albeit that the selectivity to the desired product maybecome lower. The molar ratio of the total of water, the alcohol, carbondioxide and the amine to the olefin oxide may be at most 10, inparticular in the range of from 1 to 8, more in particular from 1.1 to6, for example from 1.2 to 4. The feed fed to the second section of theprocess microchannels may comprise a total quantity of the olefin oxideand water, the alcohol, carbon dioxide and the amine of at least 60% w,in particular at least 80% w, more in particular at least 90% w, forexample at least 95% w, relative to the total weight of the said feed.The pressure may be in the range of from 500 to 3500 kPa, as measured atthe second feed channel, described hereinbefore. The reaction conditionsmay be selected such that the conversion of the olefin oxide is at least50 mole-%, in particular at least 80 mole-%, more in particular at least90 mole-%, for example at least 95 mole-%. Suitable alcohols for theconversion of the olefin oxide may be methanol, ethanol, propanol,isopropanol, 1-butanol and 2-butanol. Methanol is a preferred alcohol.Mixtures of alcohols and mixtures of water and one or more alcohols maybe used. Suitable amines for the conversion of the olefin oxide intoalkanol amine may be ammonia or a primary amine or a secondary amine.Suitable primary amines are, for example, methylamine, ethylamine,1-propylamine, 2-propylamine and 1-butylamine. Suitable secondary aminesare, for example, dimethylamine, diethylamine, ethylmethylamine,methyl(1-propyl)amine, di(2-propyl)amine and di(1-butyl)amine. Mixturesof alcohols, mixtures of amines and mixtures of water and one or morealcohols or one or more amines may be used.

The temperature of the epoxidation reaction mixture, including theolefin oxide, may be controlled before the olefin oxide enters thesecond section of the one or more process microchannels, so that theolefin oxide may adopt the desired temperature for the conversion to the1,2-diol, the 1,2-diol ether, the 1,2-carbonate or the alkanol amine.Thus, the one or more process microchannels may comprise additionally anintermediate section downstream from the first section and upstream fromthe second section, which intermediate section is adapted to control thetemperature of the olefin oxide. In particular, the reactor may compriseadditionally one or more third heat exchange channels adapted toexchange heat with the intermediate section of the said processmicrochannels.

In an embodiment, the invention provides a process for the preparationof a 1,2-diol, which process comprises

reacting a feed comprising an olefin and oxygen in the presence anepoxidation catalyst contained in a first section of one or more processmicrochannels of a microchannel reactor, which may be accomplished asdescribed hereinbefore,

converting the olefin oxide with carbon dioxide to form a 1,2-carbonatein a second section of the one or more process microchannels positioneddownstream of the first section, and

converting the 1,2-carbonate with water or an alcohol to form the1,2-diol in a third section of the one or more process microchannelspositioned downstream of the second section.

The invention also provides a reactor which suitable for the inventiveprocess for the preparation of a 1,2-diol. Accordingly, an embodiment ofthe invention provides a reactor suitable for the preparation of a1,2-diol, which reactor is a microchannel reactor comprising

one or more process microchannels comprising

an upstream end,

a downstream end,

a first section, as described hereinbefore, which is adapted to containan epoxidation catalyst, to receive a feed comprising an olefin andoxygen, and to cause conversion of at least a portion of the feed toform an olefin oxide in the presence of the epoxidation catalyst,

a second section positioned downstream of the first section, asdescribed hereinbefore, which is adapted to receive the olefin oxide, toreceive carbon dioxide, and to cause conversion of the olefin oxide toform a 1,2-carbonate, and

a third section positioned downstream of the first section which isadapted to receive the 1,2-carbonate, to receive water or an alcohol,and to cause conversion of the 1,2-carbonate to form a 1,2-diol.

The conversion of the 1,2-carbonate with water or an alcohol in thethird section of the one or more process microchannels may be a thermalconversion, but preferably it is a catalytic process. The temperaturemay be in the range of from 50 to 250° C., in particular from 80 to 200°C., more in particular from 100 to 180° C. Suitable catalysts are basicinorganic compounds, such as, for example, hydroxides of alkali metals,alkaline earth metals and metals selected from Groups 3-12 of thePeriodic Table of the Elements; basic refractory oxides, such as, forexample, basic aluminum oxide; and basic zeolites. Suitable alkalimetals are, for example, lithium, sodium and potassium. Suitablealkaline earth metals may be, for example, calcium and magnesium.Suitable metals from Groups 3-12 of the Periodic Table of the Elementsare, for example, zirconium and zinc. Other suitable catalysts are thoseknown from U.S. Pat. No. 4,283,580, which is incorporated herein byreference. More suitable catalysts comprise a metalate or bicarbonateimmobilized on a solid carrier having one or more electropositive sites.The metalate is a metal oxide anion wherein the metal has a positivefunctional oxidation state of at least +3 and it is polyvalent (i.e. themetal can have more than one valency). The polyvalent metal ispreferably selected from Groups 5 and 6 of the Periodic Table, and morepreferably from tungsten, vanadium, and, in particular, molybdenum.Typical examples of such metalate anions include anions conventionallycharacterized by the formulae [MoO₄]²⁻, [VO₃]⁻, [V₂O₇H]³⁻, [V₂O₇]⁴⁻, and[WO₄]²⁻. It is appreciated the exact formulae of these metalate anionsmay vary with the process conditions at which they are used. However,these formulae are commonly accepted as representing a faircharacterization of the metalate anions in question. The bicarbonate mayor may not be formed in situ from hydroxyl anions or carbonate anions byreaction with water and carbon dioxide. The solid carrier having one ormore electropositive sites includes inorganic carriers, for examplesilica, silica alumina, zeolites, and resins containing a quaternaryammonium, quaternary phosphonium, quaternary arsenonium, quaternarystibonium or a quaternary sulfonium cation, or a complexing macrocycle,for example a crown ether. The cation, or complexing macrocycle may ormay not be separated from the backbone of the resin by a spacer groupsuitably containing alkylene group optionally containing one or moreoxygen atoms between methylene moieties. The resin may have apolystyrene/divinylbenzene copolymer backbone, or a silica-basedpolymeric backbone, such as in polysiloxanes, or it may be a resinincorporating quaternized vinylpyridine monomers. The catalyst maycomprise molybdate [MoO₄]²⁻ or bicarbonate anions absorbed, by ionexchange from sodium molybdate or sodium bicarbonate, onto acommercially available ion exchange resin, for example Amberjet 4200(Amberjet is a trademark).

The catalyst, when present as a solid material under the condition ofthe reaction, may be installed in the third section of the one or moreprocess microchannels by known methods and applicable methods include,for example, filling at least a portion of the third section to form apacked bed, or covering at least a portion of the walls of the thirdsection with the catalyst, for example by wash coating. Some of themethods related to the installation of an epoxidation catalyst, as setout hereinbefore, may be applicable to these catalysts in an analogousmanner. In embodiments in which the catalyst represents itself as aliquid under the conditions of the reaction, the catalyst may be fed tothe third section of the one or more process microchannels through thethird feed channel and the one or more third orifices, suitably togetherwith the water and/or alcohol feed. The molar ratio of the total ofwater and the alcohol to the 1,2-carbonate may be may be less than 10,in particular in the range of from 1 to 8, in particular from 1.1 to 6,for example from 1.2 to 4. The feed fed to the third section of theprocess microchannels may comprise a total quantity of the1,2-carbonate, water and the alcohol of at least 60% w, in particular atleast 80% w, more in particular at least 90% w, for example at least 95%w, relative to the total weight of the said feed. The pressure may be inthe range of from 100 to 5000 kPa, in particular in the range of from200 to 3000 kPa, more in particular in the range of from 500 to 2000kPa, as measured at the third feed channel, described hereinbefore. Thereaction conditions may be selected such that the conversion of the1,2-carbonate is at least 50 mole-%, in particular at least 80 mole-%,more in particular at least 90 mole-%, for example at least 95 mole-%.Suitable alcohols for the conversion of the 1,2-carbonate into the1,2-diol may be methanol, ethanol, propanol, isopropanol, 1-butanol and2-butanol. Methanol is a preferred alcohol. Mixtures of alcohols andmixtures of water and one or more alcohols may be used. The conversionof 1,2-carbonate with one or more alcohols generally yields thecarbonates corresponding with the one or more alcohols, in addition to a1,2-diol. For example, conversion of ethylene carbonate with methanolgenerally yields ethylene glycol and dimethyl carbonate. The temperatureof the epoxidation reaction mixture, including the olefin oxide, may becontrolled before the olefin oxide enters the second section of the oneor more process microchannels, so that the olefin oxide may adopt thedesired temperature for the conversion to the 1,2-carbonate. Thetemperature of the carboxylation reaction mixture, including the1,2-carbonate, may be controlled before the 1,2-carbonate enters thethird section of the one or more process microchannels, so that the1,2-carbonate may adopt the desired temperature for the conversion tothe 1,2-diol. Thus, the one or more process microchannels may compriseadditionally a first intermediate section downstream from the firstsection and upstream from the second section, which first intermediatesection is adapted to control the temperature of the olefin oxide, and asecond intermediate section downstream from the second section andupstream from the third section, which second intermediate section isadapted to control the temperature of the 1,2-carbonate. In particular,the reactor may comprise additionally one or more fourth heat exchangechannels adapted to exchange heat with the first intermediate section ofthe said process microchannels and one or more fifth heat exchangechannels adapted to exchange heat with the second intermediate sectionof the said process microchannels.

In some embodiments, the invention provides a process for thepreparation of a 1,2-diol, a 1,2-diol ether, a 1,2-carbonate or analkanol amine, which process comprises reacting in one or more processmicrochannels of a microchannel reactor an olefin oxide with water, analcohol, carbon dioxide or an amine to form the 1,2-diol, 1,2-diolether, 1,2-carbonate or alkanol amine. The processes and processconditions for reacting in a section of one or more processmicrochannels of a microchannel reactor an olefin oxide with water, analcohol, carbon dioxide or an amine to form the 1,2-diol, 1,2-diolether, 1,2-carbonate or alkanol amine, as described hereinbefore, areapplicable in these embodiments.

In another embodiment, the invention provides a process for thepreparation of a 1,2-diol, which process comprises converting in one ormore process microchannels of a microchannel reactor a 1,2-carbonatewith water or an alcohol to form the 1,2-diol. The processes and processconditions for converting in a section of one or more processmicrochannels of a microchannel reactor a 1,2-carbonate with water or analcohol to form the 1,2-diol, as described hereinbefore, are applicablein these embodiments.

The 1,2-diols and 1,2 diol ethers, for example ethylene glycol,1,2-propylene glycol and ethylene glycol ethers may be used in a largevariety of industrial applications, for example in the fields of food,beverages, tobacco, cosmetics, thermoplastic polymers, curable resinsystems, detergents, heat transfer systems, etc. The 1,2-carbonates, forexample ethylene carbonate, may be used as a diluent, in particular as asolvent. Ethanol amines may be used, for example, in the treating(“sweetening”) of natural gas.

Unless specified otherwise, the organic compounds mentioned herein, forexample the olefins, alcohols, 1,2-diols, 1,2-diol ethers,1,2-carbonates, ethanol amines and organic halides, have typically atmost 40 carbon atoms, more typically at most 20 carbon atoms, inparticular at most 10 carbon atoms, more in particular at most 6 carbonatoms. Typically, the organic compounds have at least one carbon atom.As defined herein, ranges for numbers of carbon atoms (i.e. carbonnumber) include the numbers specified for the limits of the ranges.

The following examples are intended to illustrate the advantages of thepresent invention and are not intended to unduly limit the scope of theinvention. The examples are prophetic examples describing howembodiments of this invention may be practiced.

Example 1

A microchannel reactor will comprise process microchannels, first heatexchange microchannels, second heat exchange microchannels and firstfeed channels. The process microchannels will comprise an upstream end,a first section and a second section.

The first section will be adapted to exchange heat with a heat exchangefluid flowing in the first heat exchange microchannels. The second heatexchange microchannels will comprise two sets of second heat exchangemicrochannels adapted to exchange heat with the second section, suchthat in the downstream portion of the second section a lower temperaturewill be achieved than in the upstream portion of the second section. Afeed microchannel will end in the first section of the processmicrochannel through orifices. The orifices will be positioned atapproximately equal distances into the downstream direction of the firstsection from the upstream end of the microchannel till two thirds of thelength of the first section, and in the perpendicular direction theorifices will be positioned at approximately equal distancesapproximately across the entire width of the process microchannel.

The first section will comprise an epoxidation catalyst comprisingsilver, rhenium, tungsten, cesium and lithium deposited on a particulatecarrier material, in accordance with the present invention. Theparticulate carrier material will be an α-alumina having a surface areof 1.5 m²/g, a total pore volume of 0.4 ml/g, and a pore sizedistribution such that that pores with diameters in the range of from0.2 to 10 μm represent 95% of the total pore volume, and that pores withdiameters in the range of from 0.3 to 10 μm represent more than 92%, ofthe pore volume contained in the pores with diameters in the range offrom 0.2 to 10 μm.

The microchannel reactor will be assembled in accordance with methodsknown from WO-A-2004/099113, and references cited therein. The carriermaterial will be deposited on the walls of the first section of theprocess microchannels by wash coating. Thereafter, the processmicrochannels will be assembled, and after assembly silver, rhenium,tungsten, cesium and lithium will be deposited on the carrier materialby using methods, which are know per se from U.S. Pat. No. 5,380,697.

As an alternative, the microchannel reactor will be assembled, withoutprior wash coating, and after assembly the first section will be filledwith a particulate epoxidation catalyst which will be prepared bymilling and sieving a commercial HS-PLUS epoxidation catalyst, which maybe obtained from CRI Catalyst Company, Houston, Tex., USA. In order tofill the first section, a dispersion of the milled and sieved catalystin methanol will be introduced into the first section and the methanolwill be removed from the first section.

In either alternative, the first section will be heated at 220° C. byheat exchange with the heat exchange fluid flowing in the first heatexchange microchannel, while ethylene is fed through an openingpositioned at the upstream end of the process microchannels. A mixtureof oxygen and ethyl chloride (3 parts by million by volume) will be fedthrough the feed channels. The molar ratio of oxygen to ethylene will be1:1. The mixture exiting the first section and entering the secondsection of the process microchannels will be quenched in the secondsection in two steps, initially to a temperature of 150° C. andsubsequently to a temperature of 80° C. The temperature and the feedrate of the ethylene and oxygen will be adjusted such that theconversion of ethylene is 97 mole-%. Then, the quantity of ethylchloride in the mixture of oxygen and ethyl chloride will be adjusted soas to optimize the selectivity to ethylene oxide.

The ethylene oxide rich product may be purified by removing carbondioxide and unconverted oxygen and ethylene. The purified ethylene oxidemay be converted with water to yield ethylene glycol.

Example 2

A microchannel reactor will comprise process microchannels, first heatexchange microchannels, second heat exchange microchannels, third heatexchange microchannels, first feed channels and second feed channels.The process microchannels will comprise an upstream end, a firstsection, a first intermediate section, and a second section.

The first section will be adapted to exchange heat with a heat exchangefluid flowing in the first heat exchange microchannels. A first feedmicrochannel will end in the first section of the process microchannelthrough first orifices. The first orifices will be positioned atapproximately equal distances into the downstream direction of the firstsection from the upstream end of the microchannel till two thirds of thelength of the first section, and in the perpendicular direction theorifices will be positioned at approximately equal distancesapproximately across the entire width of the process microchannel.Second orifices will be positioned in a similar manner relative to thesecond section, and will connect the second feed microchannels with thesecond section of the process microchannels. The second heat exchangemicrochannels will comprise one set of second heat exchangemicrochannels adapted to exchange heat with the second section, suchthat in the second section a selected temperature will be maintained.The third heat exchange microchannels will comprise two sets of thirdheat exchange microchannels adapted to exchange heat with the firstintermediate section, such that in the downstream portion of the firstintermediate section a lower temperature will be achieved than in theupstream portion of the first intermediate section.

The first section will comprise an epoxidation catalyst comprisingsilver, rhenium, tungsten, cesium and lithium deposited on a particulatecarrier material, in accordance with the present invention. Theparticulate carrier material will be an α-alumina having a surface areof 1.5 m²/g, a total pore volume of 0.4 ml/g, and a pore sizedistribution such that that pores with diameters in the range of from0.2 to 10 μm represent 95% of the total pore volume, and that pores withdiameters in the range of from 0.3 to 10 μm represent more than 92%, ofthe pore volume contained in the pores with diameters in the range offrom 0.2 to 10 μm.

The microchannel reactor will be assembled in accordance with methodsknown from WO-A-2004/099113, and references cited therein. The carriermaterial will be deposited on the walls of the first section of theprocess microchannels by wash coating. Thereafter, the processmicrochannels will be assembled, and after assembly silver, rhenium,tungsten, cesium and lithium will be deposited on the carrier materialby using methods, which are know per se from U.S. Pat. No. 5,380,697.

As an alternative, the microchannel reactor will be assembled, withoutprior wash coating, and after assembly the first section will be filledwith a particulate epoxidation catalyst which will be prepared bymilling and sieving a commercial HS-PLUS epoxidation catalyst, which maybe obtained from CRI Catalyst Company, Houston, Tex., USA.

In either alternative, the first section will be heated at 220° C. byheat exchange with the heat exchange fluid flowing in the first heatexchange microchannel, while ethylene is fed through an openingpositioned at the upstream end of the process microchannels. A mixtureof oxygen and ethyl chloride (3 parts by million by volume) will be fedthrough the feed channels. The molar ratio of oxygen to ethylene will be1:1. The mixture exiting the first section and entering the firstintermediate section of the process microchannels will be quenched inthe first intermediate section in two steps, initially to a temperatureof 150° C. and subsequently to a temperature of 80° C. The temperatureand the feed rate of the ethylene and oxygen will be adjusted such thatthe conversion of ethylene is 97 mole-%. Then, the quantity of ethylchloride in the mixture of oxygen and ethyl chloride will be adjusted soas to optimize the selectivity to ethylene oxide.

The quenched mixture comprising ethylene oxide and carbon dioxideexiting the first intermediate section and entering the second sectionwill react in the second section in the presence of an aqueous solutionof methyltributylphosphonium iodide, to form a mixture comprisingethylene oxide and ethylene carbonate. The aqueous solution ofmethyltributylphosphonium iodide will enter the second section throughthe second orifices. The temperature in the second section is maintainedat 80° C. by heat exchange with a heat exchange fluid flowing in thesecond heat exchange microchannel.

The mixture comprising ethylene oxide and ethylene carbonate may beseparated to provide ethylene oxide and ethylene carbonate, which may bepurified separately. Purified ethylene oxide and optionally purifiedethylene carbonate may be converted with water to yield ethylene glycol.

Example 3

A microchannel reactor will comprise process microchannels, first heatexchange microchannels, second heat exchange microchannels, third heatexchange channels, first feed channels and second feed channels. Theprocess microchannels will comprise an upstream end, a first section, afirst intermediate section, and a second section.

The first section will be adapted to exchange heat with a heat exchangefluid flowing in the first heat exchange microchannels. The third heatexchange microchannels will comprise two sets of third heat exchangemicrochannels adapted to exchange heat with the first intermediatesection, such that in the downstream portion of the first intermediatesection a lower temperature will be achieved than in the upstreamportion of the first intermediate section. A first feed microchannelwill end in the first section of the process microchannel through firstorifices. The first orifices will be positioned at approximately equaldistances into the downstream direction of the first section from theupstream end of the microchannel till two thirds of the length of thefirst section, and in the perpendicular direction the orifices will bepositioned at approximately equal distances approximately across theentire width of the process microchannel. Second orifices will bepositioned in a similar manner relative to the second section, and willconnect the second feed microchannels with the second section of theprocess microchannels. The second heat exchange microchannels willcomprise one set of second heat exchange microchannels adapted toexchange heat with the second sections, such that in the second sectiona selected temperature will be maintained.

The first section will comprise an epoxidation catalyst comprisingsilver, rhenium, tungsten, cesium and lithium deposited on a particulatecarrier material, in accordance with the present invention. Theparticulate carrier material will be an α-alumina having a surface areof 1.5 m²/g, a total pore volume of 0.4 ml/g, and a pore sizedistribution such that that pores with diameters in the range of from0.2 to 10 μm represent 95% of the total pore volume, and that pores withdiameters in the range of from 0.3 to 10 μm represent more than 92%, ofthe pore volume contained in the pores with diameters in the range offrom 0.2 to 10 μm.

The microchannel reactor will be assembled in accordance with methodsknown from WO-A-2004/099113, and references cited therein. The carriermaterial will be deposited on the walls of the first section of theprocess microchannels by wash coating. Thereafter, the processmicrochannels will be assembled, and after assembly silver, rhenium,tungsten, cesium and lithium will be deposited on the carrier materialby using methods, which are know per se from U.S. Pat. No. 5,380,697.

As an alternative, the microchannel reactor will be assembled, withoutprior wash coating, and after assembly the first section will be filledwith a particulate epoxidation catalyst which will be prepared bymilling and sieving a commercial HS-PLUS epoxidation catalyst, which maybe obtained from CRI Catalyst Company, Houston, Tex., USA.

In either alternative, the first section will be heated at 220° C. byheat exchange with the heat exchange fluid flowing in the first heatexchange microchannel, while ethylene is fed through an openingpositioned at the upstream end of the process microchannels. A mixtureof oxygen and ethyl chloride (3 parts by million by volume) will be fedthrough the feed channels. The molar ratio of oxygen to ethylene will be1:1. The mixture exiting the first section and entering the firstintermediate section of the process microchannels will be quenched inthe first intermediate section in two steps, initially to a temperatureof 150° C. and subsequently to a temperature of 80° C. The temperatureand the feed rate of the ethylene and oxygen will be adjusted such thatthe conversion of ethylene is 97 mole-%. Then, the quantity of ethylchloride in the mixture of oxygen and ethyl chloride will be adjusted soas to optimize the selectivity to ethylene oxide.

The quenched mixture, comprising ethylene oxide, exiting the firstintermediate section and entering the second section will react in thesecond section in the presence of a 1%-w aqueous solution of sulfuricacid, to convert ethylene oxide into ethylene glycol. The aqueoussulfuric acid solution will enter the second section through the secondorifices. The molar ratio of water to ethylene oxide will be 3:1. Thetemperature in the second section is maintained at 80° C. by heatexchange with a heat exchange fluid flowing in the second heat exchangemicrochannel.

The reaction product, including ethylene glycol, may be separated andpurified.

Example 4

A microchannel reactor will comprise process microchannels, first heatexchange microchannels, second heat exchange microchannels, third heatexchange microchannels, fourth heat exchange microchannels, fifth heatexchange channels, first feed channels, second feed channels and thirdfeed channels. The process microchannels will comprise an upstream end,a first section, a first intermediate section, a second section, asecond intermediate section, and a third section.

The first section will be adapted to exchange heat with a heat exchangefluid flowing in the first heat exchange microchannels. A first feedmicrochannel will end in the first section of the process microchannelthrough first orifices. The first orifices will be positioned atapproximately equal distances into the downstream direction of the firstsection from the upstream end of the microchannel till two thirds of thelength of the first section, and in the perpendicular direction theorifices will be positioned at approximately equal distancesapproximately across the entire width of the process microchannel.Second orifices will be positioned in a similar manner relative to thesecond section, and will connect the second feed microchannels with thesecond section of the process microchannels. Third orifices will bepositioned in a similar manner relative to the third section, and willconnect the third feed microchannels with the third section of theprocess microchannels. The second heat exchange microchannels willcomprise one set of second heat exchange microchannels adapted toexchange heat with the second sections, such that in the second sectionsa selected temperature will be maintained. The third heat exchangemicrochannels will comprise one set of third heat exchange microchannelsadapted to exchange heat with the third sections, such that in the thirdsections a selected temperature will be maintained. The fourth heatexchange microchannels will comprise two sets of fourth heat exchangemicrochannels adapted to exchange heat with the first intermediatesection, such that in the downstream portion of the first intermediatesection a lower temperature will be achieved than in the upstreamportion of the first intermediate section. The fifth heat exchangemicrochannels will comprise one set of fifth heat exchange microchannelsadapted to exchange heat with the second intermediate sections, suchthat in the second intermediate sections a selected temperature will bemaintained.

The first section will comprise an epoxidation catalyst comprisingsilver, rhenium, tungsten, cesium and lithium deposited on a particulatecarrier material, in accordance with the present invention. Theparticulate carrier material will be an α-alumina having a surface areof 1.5 m²/g, a total pore volume of 0.4 ml/g, and a pore sizedistribution such that that pores with diameters in the range of from0.2 to 10 μm represent 95% of the total pore volume, and that pores withdiameters in the range of from 0.3 to 10 μm represent more than 92%, ofthe pore volume contained in the pores with diameters in the range offrom 0.2 to 10 μm.

The microchannel reactor will be assembled in accordance with methodsknown from WO-A-2004/099113, and references cited therein. The carriermaterial will be deposited on the walls of the first section of theprocess microchannels by wash coating. Thereafter, the processmicrochannels will be assembled, and after assembly silver, rhenium,tungsten, cesium and lithium will be deposited on the carrier materialby using methods, which are know per se from U.S. Pat. No. 5,380,697.

As an alternative, the microchannel reactor will be assembled, withoutprior wash coating, and after assembly the first section will be filledwith a particulate epoxidation catalyst which will be prepared bymilling and sieving a commercial HS-PLUS epoxidation catalyst, which maybe obtained from CRI Catalyst Company, Houston, Tex., USA.

In either alternative, the first section will be heated at 220° C. byheat exchange with the heat exchange fluid flowing in the first heatexchange microchannel, while ethylene is fed through an openingpositioned at the upstream end of the process microchannels. A mixtureof oxygen and ethyl chloride (3 parts by million by volume) will be fedthrough the feed channels. The molar ratio of oxygen to ethylene will be1:1. The mixture exiting the first section and entering the firstintermediate section of the process microchannels will be quenched inthe first intermediate section in two steps, initially to a temperatureof 150° C. and subsequently to a temperature of 80° C. The temperatureand the feed rate of the ethylene and oxygen will be adjusted such thatthe conversion of ethylene is 97 mole-%. Then, the quantity of ethylchloride in the mixture of oxygen and ethyl chloride will be adjusted soas to optimize the selectivity to ethylene oxide.

The quenched mixture, comprising ethylene oxide, exiting the firstintermediate section and entering the second section will react in thesecond section with carbon dioxide in the presence of a 1%-w aqueoussolution of methyltributylphosphonium iodide, to convert ethylene oxideinto ethylene carbonate. The aqueous methyltributylphosphonium iodidesolution and carbon dioxide will enter the second section through thesecond orifices. The molar ratio of carbon dioxide to ethylene oxidewill be 1.5:1. The temperature in the second section is maintained at80° C. by heat exchange with a heat exchange fluid flowing in the secondheat exchange microchannel.

The reaction mixture, comprising ethylene carbonate, exiting the secondsection and entering the second intermediate section will be heated inthe second intermediate section to 90° C. by heat exchange with a heatexchange fluid flowing in the fifth heat exchange microchannel.Subsequently, the reaction mixture comprising ethylene carbonate willreact in the third section with water in the presence of a 1%-w aqueoussolution of potassium hydroxide, to convert ethylene carbonate intoethylene glycol. The aqueous potassium hydroxide solution will enter thethird section through the third orifices. The molar ratio of water toethylene carbonate will be 2:1. The temperature in the second section ismaintained at 90° C. by heat exchange with a heat exchange fluid flowingin the third heat exchange microchannel.

The reaction product, including ethylene glycol, may be separated andpurified.

1. A process for the preparation of an alkylene glycol by the reactionof a corresponding alkylene oxide and water, which process comprises a)flowing alkylene oxide and water through a microchannel reactor, whereinthe alkylene oxide and water undergo an exothermic reaction to form thecorresponding alkylene glycol, b) transferring heat from themicrochannel reactor to a heat transfer medium, and c) recovering thealkylene glycol product from the microchannel reactor.
 2. A process asclaimed in claim 1, wherein the microchannel reactor contains a catalystsuitable for the catalytic hydrolysis of alkylene oxide.
 3. A process asclaimed in claim 2, wherein the catalyst is a homogeneous catalystpresent in the reaction mixture.
 4. A process as claimed in claim 2,wherein the catalyst is a heterogeneous catalyst present as a solidcatalyst in, or as a coating on the walls of, one or more processmicrochannels present in the microchannel reactor.
 5. A process for thepreparation of a mono-alkylene glycol by the reaction of a correspondingalkylene oxide and water, which process comprises a) reacting thealkylene oxide and water in a first reactor under a first set ofconditions and in the presence of a catalyst so as to achieve vaporphase conversion to the mono-alkylene glycol, b) altering the conditionsin the first reactor to a second set of conditions whereby glycolsdeposited on the surface of the catalyst are removed, c) re-establishingthe first set of conditions in the first reactor in order to repeat stepa), and d) recovering the mono-alkylene glycol from the vapor phasemixture produced in step a) and/or step b).
 6. A process as claimed inclaim 5, wherein the first reactor is a microchannel apparatus.
 7. Aprocess as claimed in claim 5, wherein step a) is carried out using theprocess as claimed in claim
 1. 8. A process as claimed in claim 5,wherein the conditions of step b) are altered by a change oftemperature.
 9. A process as claimed in claim 5, wherein the conditionsof step b) are altered by a change of pressure.
 10. A process as claimedin claim 5, wherein the conditions of step b) are altered by a change oftemperature and pressure.
 11. A process as claimed in claim 5, whereinthe alkylene oxide is ethylene oxide and the mono-alkylene glycolprepared is mono-ethylene glycol.